Leslie Gesneria was a volunteer/mercenary for the Life Foundation, an organization that was preparing for the M.A.D. (Mutually Assured Destruction) fallout of the Cold War and sought to provide a comfortable life for their wealthy clients after the impending nuclear holocaust. Leslie was one of the organization's security force members who was chosen to be made into one of the superhuman police force members for the utopian future that the Life Foundation sought to bring about. This was done by forcibly extracting multiple offspring from the alien creature known as Venom, after which the offspring were artificially aged to maturity. Leslie was bonded with one of these symbiote offspring and became one of the Life Foundation's Guardians.
Agony was created by David Michelinie, Ron Lim, Sam DeLarosa and Al Milgrom in 1993 and first appeared in Venom: Lethal Protector #4.
The symbiote name "Agony" came about rather unofficially due to a female symbiote character in a Venom toy line. While fan-based, this name has since stuck as in 2012's Carnage U.S.A. it was officially identified by the name of Agony for the first time.
Major Story Arcs
During Venom's time as Lethal Protector of San Francisco, Agony and her siblings were defeated by Venom and Spider-Man.
It was later revealed that the symbiotes had survived due to efforts by the Life Foundation. They broke Eddie Brock out of prison and kidnapped him in a last ditch effort to communicate with their alien "others." Unfortunately Eddie refused to aid them, due to Carnage's example that his "children" became psychopathic killers. Shortly after Brock's refusal, Leslie was stabbed from behind and killed. The rest of her symbiote siblings mourned her passing, especially Carl Mach, who sought to kill Brock out of revenge when it was assumed that he was the one who'd killed Leslie. It's later revealed however that Scream, having snapped from her schizophrenia and her symbiote's influence, killed Leslie, believing that the symbiotes and any who host them were evil. She went on to kill Carl and the rest of the symbiote hosts even after her ruse was revealed.
Agony survived, and was imprisoned/experimented upon in the Vault along with its siblings (except Carnage and Scream). The symbiotes eventually merged together, and bonded with a man known as Scott Washington to form Hybrid.
In Carnage: USA, the Hybrid symbiote was revealed to have been forcibly separated behind the scenes. The Agony symbiote, along with its siblings, were rendered catatonic as a result of the trauma of the separation. Covert Government Mercury Team, trained with them to teach them specialized tasks. Agony was teamed up with Lieutenant James Murphy, Navy Seal as a brace for rail gun weighing over 800 pounds.
They were called on as a contingency team when the Avengers failed to free the town of Doverton, Colorado from Carnage's control.
Deadpool vs. Carnage
In Deadpool vs. Carnage, Deadpool stole the symbiotes from a government facility to help him combat Carnage. After defeating Carnage he puts the symbiotes on a dog and instructs it to take them back to the government.
King in Black
The dog that Deadpool left the symbiotes in the care of was distracted by a crying young girl named Sadie. She was having family problems, so the symbiotes bonded to her family (with Agony bonding to Sadie’s mother) to keep them together. Piloting their bodies, they make their way to Manhattan to assist in the Knull Invasion.
Under Carnage’s orders, they hunt down Dylan Brock and Normie Osborn. Unfortunately, they were left with The Maker, who was currently inventing ways of ending the symbiote threat. While Dylan and Normie hid, The Maker was able to remove them from their hosts and stick both the hosts and the symbiotes in stasis pods.
Dylan was growing distrustful of Maker and tried shooting his and Normie’s way out. Instead of hitting Maker though, he freed the symbiotes from their stasis pods, allowing them to all bond to Maker. This hybrid chased them into the streets where Spider-Man had led a few Avengers to help. They are eventually chased off by Hawkeye’s multiple anti-symbiote arrows.
Separated, they continued to look for Dylan in New York during Knull’s invasion. They are confronted by their sibling, Scream, who is now bonded to Andi Benton. Scream and Andi were defending the various children the symbiotes were assaulting. The symbiotes combined into Hybrid again to take on Scream, but Andi’s Hell-Mark powers ripped them apart. Wounded, they escape through the sewers
After the events of King in Black, Agony bonds to Gemma Shin, the Deputy Director of Communications for Peter Krane's campaign. Once she makes a bond with the symbiote, she is promoted to Director of Communications under Carnage, who is bonded to Krane's son. Together, with other Life Foundation symbiotes, they plan on assassinating Sen. Krane at his own anti-alien demonstration.
When Flash Thompson's team and the Guardsmen get involved, most of her siblings are detained by Alchemax. Agony and Carnage got away, with Agony retaining a position in the Krane administration, now that a Carnage-less Arthur Krane was given his father's old position.
After Kingpin outlaws superheroes in New York, Agony is deputized to his Thunderbolt Units, the only sanctioned superhero team in the city. Besides keeping the peace, Agony and the Thunderbolts main mission was searching New York City for The Purple Children so that Kingpin could increase the amount of Purple Man power he was harnessing.
She and her team were able to capture all but one of the Purple Children, which was enough for Kingpin to undo the psychic blind spot that was stopping Fisk from remembering Daredevil's true identity. Once he had the information again, he abandoned all his plans for revenge, but first cause a riot distraction by mesmerizing the Thunderbolts, including Agony, into attacking the citizens.
She was eventually captured and imprisoned after Luke Cage beat Fisk in the election for Mayor. She attempted to escape with her fellow Thunderbolts, but Cage's new Thunderbolts, led by Hawkeye, recaptured her.
Agony was broken out of jail by Daredevil and his new team, The Fist, a ninja clan that he founded with Elektra to confront The Hand. She, along with a number of other inmates, agreed to join their ranks for their freedom. Through training with Elektra, Gemma Sin was learning how to control the symbiote and ultimately used it to save brain-washed former member, Bullet, from The Hand.
Unfortunately, their island fortress was attacked by both NY crime family, The Stromwyns, and The Avengers. The Avengers showed up to arrest Elektra for the death of the president, but the Stromwyns dropped the re-cid drug on the island, causing members of The Fist to riot. Despite Agony being successfully arrested by The Avengers, she was quickly released when Daredevil forced the Stromwyns to use their connections to do so.
Agony first appeared in video-games as a boss in Venom & Spider-Man: Separation Anxiety, she was fought at the end of multiple levels of that game with various combinations of her "brothers and sister".
In 2013, Agony received an unexpected nod when she, not her Mercury Squad counter-part, was hinted as being in Marvel Avengers Alliance Season 2, VIA the Days of Future Past homage teaser. She, along with Reptil, Razorfist, Captain Ultra, Doctor Bong, Yoshida, Psyklop, Razorback, and others were all tagged with the ominous "Slain" label, much as many of the X-Men were on the cover this image references.