Needed to get this shit out of the way, so @emperordmb would start that Windu blog. Anyways, can't post images on the site, so I'll just be using a description. If that don't satisfy you, then Google is your friend. With that out of the way, respect Onimi.

The man she had thought a master shaper was deformed. Not scarred or modified as sacrifice to the gods, but misshapen as one born cursed by them. One eye lolled lower on his face than the other, and part of his skull was oddly distended. His mouth was a twisted slash. His long, lean limbs twitched with a sort of mad delight.

New Jedi Order: Edge of Victory: Rebirth

Art of the Small

Through Art of the Small, Onimi was capable of transmuting his bodily fluids, and producing a brew of fast-acting and deadly toxins.

But the struggle had nothing to do with size and less to do with brute strength. Onimi's true potency lay in his abilities to amplify the electric current that flowed through his body, or-like Vergere-to call on his refined metabolism to fashion molecules and compounds, and deliver them through his curving yellow fingernails, his single fang, his blood, sweat, saliva, and breath. But where Vergere had learned to produce emollients and healing tears, Onimi was capable of producing a brew of fast-acting and deadly toxins.

New Jedi Order: The Unifying Force

Jacen Solo considers Vergere's mastery of Art of the Small to be merely that of an adept compared to Onimi's, implying he is capable of replicating all of her feats with the ability.

Compared to the former shaper's mastery of Yuuzhan Vong bioscience, Vergere had been a mere adept. He flew at Jacen with hands upraised and mouth ajar. Jacen lifted his hands in defense and he and Onimi met with blinding discharges of electrical energy that entangled both of them in a flashing web.

New Jedi Order: The Unifying Force

With only a "small taste" of his poison, Onimi completely paralyzed Jaina Solo in only a few moments.

Bent over her, he wrenched the lightsaber from her hands and tossed it aside. Then, grabbing her by the right ankle, he sent her sliding across the floor. She hit the wall solidly, but sprang to her feet. Shimrra's companion was on her just as quickly, driving his fanglike tooth into her right arm as his powerful hands pressed her to the wall. Even before he stepped back, she had lost feeling and movement in her arm, and now she could feel the numbness beginning to spread like a dark tide, coursing through her armpit into her upper chest, spreading across her chest and into her other arm, up into her neck and head, and down through her torso and legs. She became as pliant as soft leather.

-

"I know you can hear me," he said in a guttural Basic, "because I gave you only a taste of the poison encapsulated in my fang. Just enough to render you inert." With a glance at the console he enlivened additional living instruments and systems. It was obvious that he was preparing the vessel for launch. When the bridge began to vibrate with anticipation, the Shamed One nodded in satisfaction and turned to her once more.

New Jedi Order: The Unifying Force

Onimi transmutes his sweat into hallucinogens which he sends through Jacen Solo's skin and capillaries, and coursing through his bloodstream. He wafts poison into his forced sighs, and transmutes his saliva into poison.

The transmutated secretions from Onimi's palms and fingertips sent hallucinogens through Jacen's skin and capillaries, and coursing through his bloodstream. Onimi's paralyzing fang struck repeatedly for Jacen's temples and neck. Poison wafted on his forced sighs and rode within the droplets of his frothing saliva. But the Jacen that the Supreme Overlord had in his taloned grip was not there. Where once Jacen had been unable to find Onimi through the Force, now it was Onimi who couldn't find Jacen.

New Jedi Order; The Unifying Force

Onimi produces a corrosive poison so potent, that when Jacen Solo turns it against him, it reduces him to nothing more than a puddle of foul hydrocarbons.

But life deserted him just as quickly. He slid to the deck as if his bones had dissolved. Poured from his mouth, eyes, and ears, corrosive fluids began to consume him, leaving nothing more than a puddle of foul hydrocarbons, which the yorik coral deck absorbed as it might a stain. Immediately the vessel spasmed, as if it had been struck by turbolaser fire, or had in fact sustained a kind of stroke. Color and warmth drained from the living console, and the instruments took on an arthritic look.

-

Nom Anor watched in awe as Onimi disappeared into the deck of the bridge, his body dissolved by whatever corrosive poisons he had fabricated to use against Jacen Solo.

New Jedi Order: The Unifying Force

Telepathy

Onimi seemingly reads Jaina Solo's thoughts.

Jacen! Uncle Luke! she called through the Force. When she reached out for them, her mind was assaulted with scenes of violence. Jacen and Luke had overcome great odds, but both of them were injured. Except through their minds, she couldn't perceive the warriors, but she grasped that most of them were dead.

Abruptly, the twisted figure turned from the console to face her, almost as if he had read her mind.

New Jedi Order: The Unifying Force

Onimi turned Shimrra into his puppet. At first, he compelled him to initiate the Vong conquest of the galaxy, then bade him to make Onimi his familiar, and, as his telepathic abilities increased, completely subjugated his mind.

"Only by means of the powers you conferred on me was I able to reach out for Shimrra and make him my puppet! My most audacious act yet. But when I saw that you were either powerless to prevent it or welcoming the opportunity to do open battle with me, I knew that I was right to attempt to overthrow you in the same way.

"I compelled Shimrra to announce that a galaxy had been found for the taking. I bade him to install me as his familiar. And as my telepathic abilities increased, he disappeared-except of late, when my preoccupation with defeating you allowed what remained of Shimrra to re-emerge.

New Jedi Order: The Unifying Force

But it turns out Shimrra was never the true power behind the Yuuzhan Vong. The real mastermind was the twisted, snickering jester who sat at Shimrra’s feet: Onimi. Jaina chases the Shamed One into the upper passages of the citadel. The twisted Yuuzhan Vong hides Force abilities—a former shaper, Onimi discovered how to reconnect to the Force when in his experiments he grafted yammosk tissue to his brain. Able to manipulate the minds of others, Onimi made Shimrra his puppet as he commanded the invasion of the galaxy.The Essential Reader's Companion: Star Wars

Onimi knocked Jaina unconscious and reached an escape ship. When Jaina regained her senses aboard the getaway vessel, Onimi revealed that he had been the power behind the throne all along. As a former master shaper who had grafed telepathic yammosk brain cells into his own cortex. Onimi was a literal puppet master who could force even Shimrra to do his bidding. New Essential Guide to Chronology Online

Telekinesis

Possibly via usage of telekinesis, Omini caused quakes that threatened to topple the Citadel.

Jacen realized the truth. Onimi had overseen the warriors in the throne room below. Onimi, not the dhuryam, had been responsible for the quakes that had nearly toppled the Citadel...

New Jedi Order: The Unifying Force

Onimi hurls a blur of objects at Jacen Solo.

On the bridge of the vessel whose every component answered to him, Onimi sent a blur of objects racing for Jacen, beginning with the carved idols that flanked Jaina: cloaked Yun-Harla, many-armed Yun-Yammka, thousand-eyed Yun-Shuno, and the rest.

New Jedi Order: The Unifying Force

Onimi creates cracks in the bulkheads and ceiling via usage of telekinesis.

Reaching deeper into himself, the Supreme Overlord used his telekinetic powers to create cracks in the bulkheads and ceiling, hoping to add chunks of uprooted yorik coral to his conjured storm.

New Jedi Order: The Unifying Force

Force Sense

Onimi views Jaina Solo through the Force, and sees the glow of the divine in her. He reveals he's also saw Luke Skywalker, Jacen Solo, and Tahiri Veila through the Force, and has seen the glow of the divine in them as well.

Onimi looked hard at Jaina.

He's seeing me through the Force! she told herself. As much as the realization shocked and confused her, it gave her hope.

"Even now I can see the glow of the divine in you, Yun-Harla. As Yun-Yammka glows in the Jeedai called Skywalker; Yun-Shuno in the Jeedai called Jacen; Yun-Ne'Shel in the Jedi called Tahiri..."

New Jedi Order: The Unifying Force

Onimi senses Shimrra's death, and that it was the Jedi who killed him.

"Shimrra is dead," he announced. "Your god-cohorts have killed him, Yun-Harla. Now let us hope they will pursue me, as well. Then not only will I have the satisfaction of outwitting you at Zonama Sekot, but I will also have the pleasure of killing you, as my first act in exterminating everyone and everything in this foul galaxy."

New Jedi Order: The Unifying Force

Force Lightning

Possibly a usage of Force-Lightning, or Art of the Small, when Onimi clashes with Jacen Solo, blinding discharges of electrical energy entangle the both of them in a flashing web.

Compared to the former shaper's mastery of Yuuzhan Vong bioscience, Vergere had been a mere adept. He flew at Jacen with hands upraised and mouth ajar. Jacen lifted his hands in defense and he and Onimi met with blinding discharges of electrical energy that entangled both of them in a flashing web.

New Jedi Order: The Unifying Force

Strength

Onimi jumps on Jaina Solo, driving her to the floor, then wrenches her lightsaber from her hands, showcasing physical dominance over her.

Her instincts came alive even before she glanced up into the ladder well. The Shamed One was already plummeting directly for her. She raised her lightsaber over her head, but the Yuuzhan Vong managed to evade the blade and land feetfirst on her shoulders, driving her to the deck. Bent over her, he wrenched the lightsaber from her hands and tossed it aside.

New Jedi Order: The Unifying Force

Onimi sends Jaina Solo sliding across a room, causing her to hit a wall solidly.

Then, grabbing her by the right ankle, he sent her sliding across the floor. She hit the wall solidly, but sprang to her feet.

New Jedi Order: The Unifying Force

Pound for pound, Onimi is physically more powerful than Jacen Solo.

But as fast as the fissures formed, Jacen repaired them, and those chunks that were torn away he ordered the vessel to cement in place. Mismatched eyes opened wide in disbelief, Onimi charged, his feet moving so rapidly that he might have been gliding across the deck. Though crippled by the deformations that had resulted from poorly healed enhancement surgeries and the consequences of experimental escalations, the former shaper was still taller than Jacen and pound for pound more powerful.

New Jedi Order: The Unifying Force

Speed

Onimi evades Jaina Solo's blade.

Her instincts came alive even before she glanced up into the ladder well. The Shamed One was already plummeting directly for her. She raised her lightsaber over her head, but the Yuuzhan Vong managed to evade the blade and land feetfirst on her shoulders, driving her to the deck.

New Jedi Order: The Unifying Force

Onimi moves at comparable speeds to Jaina Solo, crossing a room in the time it takes her to jump back to her feet.

Bent over her, he wrenched the lightsaber from her hands and tossed it aside. Then, grabbing her by the right ankle, he sent her sliding across the floor. She hit the wall solidly, but sprang to her feet. Shimrra's companion was on her just as quickly, driving his fanglike tooth into her right arm as his powerful hands pressed her to the wall.

New Jedi Order: The Unifying Force

Onimi runs so fast that he seemingly glides across a deck.

But as fast as the fissures formed, Jacen repaired them, and those chunks that were torn away he ordered the vessel to cement in place. Mismatched eyes opened wide in disbelief, Onimi charged, his feet moving so rapidly that he might have been gliding across the deck. Though crippled by the deformations that had resulted from poorly healed enhancement surgeries and the consequences of experimental escalations, the former shaper was still taller than Jacen and pound for pound more powerful.

New Jedi Order: The Unifying Force

Combat Skill

Onimi displays some proficiency with an amphistaff, incapacitating Sal-Solo with a single, efficient slash to his kidney.

"Let us find out," Shimrra said. He made a slight gesture, and Onimi rose from his place at the foot of Shimrra's dais. In the dim light Nom Anor saw, coiled in the Shamed One's hand, a baton of rank, the officers' version of the amphistaff. He was shocked to discover that Shimrra permitted his familiar to carry weapons.

But who else would be more trustworthy? Nom Anor thought. Onimi must know that if Shimrra is killed, his own death will surely follow.

Onimi stepped behind Sal-Solo and flung out his lank arm. The whiplike baton froze into its solid form, now a lean staff, and Onimi with a single efficient swing slashed the weapon into Sal-Solo's left kidney.

New Jedi Order: Ylesia

Onimi swiftly overwhelms Jaina Solo.

Half a dozen dilating hatches led to adjacent cabin spaces, and yet another stairway-more a ladder-climbed into what could only be the vessel's cockpit. Jaina rushed to grab hold of the ladder as the bunker tilted. From below came the sounds of bodies being hurled first one way, then the other. In the midst of the swaying she heard the thrum of Luke's and Jacen's lightsabers, and the agonized cries of at least two slayers. There was no sign of Shimrra's companion in the ready room, and no dilating locks that might have been opened to access other areas of the sphere, so the misshapen figure had to have climbed into the cockpit.

Her instincts came alive even before she glanced up into the ladder well. The Shamed One was already plummeting directly for her. She raised her lightsaber over her head, but the Yuuzhan Vong managed to evade the blade and land feetfirst on her shoulders, driving her to the deck.

Bent over her, he wrenched the lightsaber from her hands and tossed it aside. Then, grabbing her by the right ankle, he sent her sliding across the floor. She hit the wall solidly, but sprang to her feet. Shimrra's companion was on her just as quickly, driving his fanglike tooth into her right arm as his powerful hands pressed her to the wall. Even before he stepped back, she had lost feeling and movement in her arm, and now she could feel the numbness beginning to spread like a dark tide, coursing through her armpit into her upper chest, spreading across her chest and into her other arm, up into her neck and head, and down through her torso and legs. She became as pliant as soft leather.

She remained alert but her lips and tongue couldn't form words. Her eyelids fluttered, and sounds grew indistinct. One thought kept repeating itself in her mind as she slipped into the blackest of voids. Before he had dropped on her, she had sensed him through the Force!

New Jedi Order: The Unifying Force