"They call me terrorist, radical, zealot because I obey the ancient laws of my people, the Kree....and punish those who do not. Because I do not forgive your people for taking the life of my father, and his father, and his father before him. A thousand years of war between us will not be forgotten!"― Ronan the Accuser
Ronan the Accuser (the primary antagonist in Guardians of the Galaxy) was a radical member of the Kree race who was disgusted by a peace treaty made between the Kree Empire and Xandar. A ferocious, genocidal militarist, Ronan attempted to eradicate the Xandarians by forging an alliance with the Mad Titan Thanos, offering the Orb in exchange for the destruction of Xandar. After a long search, Ronan finally acquired the Orb but, having seen it's true destructive capabilities, decided against giving it to Thanos, choosing to take the Orb's power for himself. Using his new-found power, he attacked Xandar, but was eventually defeated and killed by the combined strength of the Guardians of the Galaxy.
- Superhuman physical attributes: as a member of the Kree race, Ronan possessed physical abilities enhanced beyond those of the humans, including superhuman strength and durability.
- Expert Tactician: Ronan is an experienced and exonerated member of the Kree military, and as such, he is a skilled strategist. He led the Sakaarns during the Battle of Xandar.
- Master Combatant: As a warrior and military figurehead, it is only natural that Ronan would have extensive combat and military training. He had very impressive hand to hand skills, easily countering Drax the Destroyer's hits with little effort and defeating him in battle twice. He also trained Gamora and Nebula to become expert warriors.
- Universal weapon: Ronan the Accuser was the wielder of the powerful hammer known as the Universal Weapon, a large staff-like war hammer. In addition to using it as a melee weapon, he can also fire some sort of force that is capable of snapping a person's neck by twisting their head 180 degrees, as he did to The Other.
- Kree Armor: Ronan used a technologically advanced battlesuit that enhanced his strength and durability to levels higher than they already were. The Armor was powerful enough not to shatter when shot in the chest plate with the Hadron Enforcer, although Ronan's strength had been considerably increased by this stage.
Ronan kills The Other using a concussive blast from his Universal Weapon. The Other has been described as extremely powerful by the directors of GOTG, even in comparison to someone like Loki.
Easily dodges and parries Drax's first attacks, then drops him to the ground with a simple one-handed shove.
Again, Ronan easily dodges and blocks Drax's attacks, then proceeds to backhand him with incredible force (as if Drax were shot out of a cannon) a fair distance into a building (which actually does a fair bit of damage to the building itself).
Ronan casually stops Drax's attack and forward momentum and sends him flying back to where the attack began, with a simple one armed blow.
Yet again, Ronan easily dodges Drax's attacks, then proceeds to disarm him of both of his knives with two well placed strikes (one was more of a block I guess).
Grabs Drax by the throat with one hand, and is so strong that Drax cannot break out of the grip. Ronan then no-sells literally all of Drax's punches, save for the final one that bugged him (Ronan) enough for him to get pissed off and body-slam Drax. This body-slam takes Drax completely out of the fight.
Ronan proves to be powerful enough to hold an infinity stone directly for a time, and to safely be able to use its power by channeling it through his Universal Weapon. This stone has been shown to almost instantly kill normal people, even killing a large group of people after mere seconds of exposure despite them sharing the power between all of them. Oh, and for good measure, he now has the confidence to directly challenge Thanos (not that this means much, but it was a cool moment).
Using his now power gem infused Universal Weapon, Ronan blasts a hole right through the shielding technology of the Xandarian fleet, completely disabling it and destroying possibly hundreds of the Xandarian ships.
Ronan tanks this RPG directly to the chest, and seconds later, gets back up with no apparent injuries.
Ronan sends the Guardians flying backwards with this concussive blast.
Ronan, with one arm, easily stops Drax's charge and lifts him above his head.
Ronan survives this ship crashing into him. It seems likely that he was KO'd (or maybe just temporarily trapped under a bunch of rubble), but he reemerges for the final showdown with the Guardians on the surface of Xandar with no apparent injuries.
The power gem has the ability to destroy at the very least the entire surface of a planet. Everything in the movie points to Ronan possessing this level of power, despite the fact that he never actually got the chance to use it in the movie.
All in all, despite his relatively few showings, Ronan is clearly established as being one of the top tiers in the Marvel Cinematic Universe (at least at the moment). The power he wielded after merging his Universal Weapon with the power gem combined with his natural physical capabilities makes him quite the formidable combatant and definitely worthy of people's respect.