Gabriel

"I'm an angel. I kill firstborns while their mamas watch. I turn cities in salt. I even, when I feel like it, rip the souls from little girls. And from now 'til kingdom come, the only thing you can count on in your existence... is never understanding why..."
~ Gabriel

He is the angel of death, vengeance, and revelation, as well as one of Heaven's elite Archangels. In the third movie, he has transitioned into a protagonist who redeems himself for his evil actions.

Gabriel wished to win the heavenly war against Lucifer and his hellish minions, and he was greatly angered by God for His inaction and silence about the stalemate in the war against Hell, and by the remaining angels for their blind obedience to God and their lack of free will. Thus, he decided to take matters into his own hands, even if he had to betray His creator and the rest of his creation. He was very narcissistic and never reconsidered his mission even once (until his redemption, that is). He always thought that the end justifies the means, however insane they are.

Speaking about God's creations, Gabriel loathed humanity and killed many people for sometimes no reason thorough the ages, proudly boasting that he murdered newborns in front of their mothers; he also didn't think much of his minions, killing them when they outlived their usefulness and torturing them when they failed him, as seen when he burned Izzy's hand after her suicide attempt. By the second installment, his hatred of humans worsened, to the point that he was willing to compromise the birth of a Nephilim prophesized to bring prosperity to Heaven, simply because he was part human, showing how hypocritical he was. He also brutally tortured and murdered any angel who stood against him with no second thought. His favorite methods of execution included beatings his victims to death and setting them on fire.

Also, despite sadistically tormenting beings that couldn't harm him, he was no coward, fighting powerful beings such as angels if he had to and even laughing at Lucifer's face. He also didn't flinch when Archangel Michael threatened him to suffer a "harsh punishment" for his various crimes and rebellion.

Since he didn't care much about "down here", Gabriel would've gladly caused the biblical Apocalypse and destroyed the whole Earth (if not the whole universe) just to achieve the war. Given his very sadistic nature and genocidal intends, Lucifer remarked that Gabriel was no better than him. Gabriel was also once again very hypocritical given that he criticized Lucifer for his obsession with God and the Heavens, while Gabriel himself constantly thought about God, and wanted to take over Heaven as a way to overthrow God and make Him suffer for his inaction.

Deep down, Gabriel was very insecure and wished that God renewed His interest in His angels and loved them as He did when He created them, which also explains why he hated humanity so much as Gabriel thought that God preferred them over the angels. This also highlights his supremacist mindset, believing angels to be superior to mortals because of their powers, infinite lifespan, and wisdom. He was greatly wronged anytime his mission or even loyalty towards God and the Heavens was put in question.

After spending twenty years as a human as punishment for his various misdeeds, Gabriel completely changed and became much humbler, nicer, and (quite literally) more human. Instead of desiring humanity's destruction, Gabriel sought to protect them and earned redemption for his actions, by looking over Danyael, the Nephilim that he failed to murder in the previous installment. As Danyael's girlfriend lay dying, Gabriel did his best to comfort her, unable to do anything else in his powerless state. Upon earning his powers back, he was kind enough to heal her injuries and save her.

Gabriel was an immensely powerful archangel who possessed an impressive array of powers, given his celestial origins:

Nigh-Omnipotence: Gabriel is an archangel of immense power. He has, as he boasted, turned cities to salt and ripped the souls of humans from their bodies.
Immortality: Gabriel was present at the creation of the universe.
Superhuman Strength: Gabriel is noticeably physically stronger than most humans; he casually overpowers any mortal adversary that opposes him.
Superhuman Agility: Gabriel has an unnatural balance.
Healing Factor: Gabriel, like all angels, has the power to spontaneously regenerate his body from any injury. Wounds from most objects, even bullets, heal in seconds without causing him any lasting discomfort. He can only be killed by having his heart ripped out.
Cosmic Awareness: While not omniscient, Gabriel has immediate knowledge of certain things.
Supernatural Perception: By licking the remains of his own blood, Gabriel was able to identify and find Simon.
Perception Alteration: Gabriel can make people see and hear things that are not really there.
Resurrection: As the angel of death, Gabriel can call back the souls of the recently deceased to their bodies and return them to life. He can grant them a form of immortality by refusing to let them die until they fulfill their obligations to him.
Healing: Gabriel can heal a person's wounds, even fatal ones. After regaining his powers, he was able to heal Danyael's girlfriend of her fatal injuries.
Pyrokinesis: Gabriel can set fire to objects and people with only a thought.
Flight: Gabriel can fly with his wings.
Shapeshifting: Gabriel can transform into a flock of luminous white doves. Like all angels, he hides his wings with this ability.
Sedation: He can put humans to sleep just by touching their foreheads.