The Atoner: During Mark Waid's run, Banner is committed to do far more good for the world than the Hulk has ever done harm.
Badass: While out of his mind after being completely separated from the Hulk, he demonstrated just how badass he can be, creating an arsenal of superscience weapons that allowed him to fight on equal terms with the green giant. He does it again in Fall of the Hulks, and any other time that he's depowered.
Can't Stay Normal: No matter how many times he is depowered, Bruce will always transform back into the Hulk.
The Chessmaster: Particularly during the Fall of the Hulks storyline, where Banner manages to outmanouvere all of the smartest people in the world to save Betty and the Avengers.
Green-Eyed Monster: Jokes aside, the Indestructable Hulk series reveals one of his major issues with being the Hulk is that he's constantly in the shadow of men like Tony Stark and Reed Richards- they'll be remembered by history as men of science, while he'll be remembered as the Hulk, even though he has as much to offer the world as either of them. The fact that neither treats him as an equal doesn't help matters.
Guile Hero: Bruce is one of the smartest people in the world, and it shows, particularly in Fall of the Hulks, where he plays the likes of Dr. Doom and The Leader with panache.
The Idealist: During Mark Waid's run it is revealed that Bruce was originally a pacifist who wished to develop clean energy sources, but couldn't receive funding, so he developed a bomb for the military instead, with the hope that he could harness gamma power for this purpose. He also consistently used his genius to develop technology for the betterment of mankind during this period, and signed up the Hulk to help the Avengers, SHIELD, and the Illuminati.
I Lied: Happens a lot during The Fall of the Hulks, as he manipulates the superhero and supervillain communities to save Betty and the world from The Leader.
Not That Kind of Doctor: Played with, while Bruce doesn't have a doctorate in medicine, he was originally a med student. Because of this, he is capable of providing medical care in a pinch, such as when he gave his cousin Jen that blood transfusion.
Science Hero: Whenever he has to save the day independent of the Hulk, you can bank on a wide variety of gadgetry and scientific theorising being involved.
Self-Made Orphan: Although it was an accident, and self-defense, while visiting the grave of his beloved murdered mother, he did kill his own father.
Berserk Button: He hates being compared to any of the green Hulks. While the Blob had managed to restrain him in a bearhug, once the Blob quipped that the Hulk was barely stronger than him back when he was green Joe immediately broke free and proceeded to immediately curb stomp the Blob.
Villain Protagonist: He was a mafioso, a torturer, a bully, a murderer, a mercenary, a lecher, a Break Them by Talking-giver to broken people, and proud of all of it. He mellowed out during the Dale Keown run.
Good Samaritan: Ran multiple charity organisations, research for cancer cures provided food for starving children, shelters and education for war-refugees, supported revolutions against tyrants of oppressed peoples through much lesser loss of lives than real world military interventions can manage, and so on.
Humanoid Abomination: He has essentially gradually turned into one, both in terms of raw power, destructive nature, and turning even more powerful from both dark magic and nuclear explosions, as a force of pure destruction merging forces of both science and mysticism. More openly after picking up one of the hammers of "The Worthy". This is especially true when he goes full on "Worldbreaker". For example, he went Worldbreaker in the Dark Dimension and reduced most of the realm into floating rubble.
World's Strongest Man: Word of God is that World War Hulk Green Scar was "stronger than any mortal and most immortals in the Marvel universe", and as always, except the Onslaught fight, he was holding back a lot so he wouldn't risk to destroy his entire home reality. Hulk's full level of power is of a literally infinite scale going by the Beyonder, and that he overpowered a villain with the power of two Celestial-level beings.
Betty Ross/Harpy/Red She-Hulk
Bruce Banner's first and most enduring Love Interest, Betty Ross is the daughter of General Ross, one of the Hulk's longtime foes. She's since been through almost as much trauma as Banner himself having married, and then divorced Glenn Talbot, lost her relationship with her father, been turned into the supervillainess Harpy by MODOK, nearly died of cancer given to her by the Abomination, and finally been turned into the Red She-Hulk by The Leader, who then forced her to fight against most of the Marvelverse's heroes. Currently back in control of herself, Betty is now struggling to establish a new sense of self.
Self-Made Orphan: Narrowly averted. Betty almost killed the Red Hulk, only to realise he was her father and stop in time.
Split Personality: The degree to which she retains control over Red She-Hulk varies a lot. Sometimes it's just an angrier Betty, while at others it is an entirely different persona whom she fears losing control over.
Wouldn't Hurt a Child: Broke his oath to the emperor when he refused to kill the emperor's son on his orders. Considering that son grew up to be the Red King, that might not have been the best move, but he stands by it.
A Korean-American Teen Genius whose life was saved by the Hulk. He sides with the Hulk during the events of World War Hulk and teams up with Hercules afterwards. He teams up with Bruce Banner again after Hercules loses his powers during the events of Chaos War
A young woman with powers who may or may not be Bruce Banner's biological daughter.
Luke, I Might Be Your Father: Carmilla learns from Amadeus that she might be the daughter of Bruce Banner and Monica Rappaccini, Scientist Supreme of A.I.M. However, this has yet to be confirmed one way or another.
Required Secondary Powers: Complete immunity to all known toxins and toxic environments due to, quote, "ridiculous" amount of redundant physiological defenses. Interestingly enough this part was intended in her design where the former ability to poison others was an unexpected mutation.
Tragic Monster: One story arc has him hiding out in the sewers and befriending a group of homeless people, who see him as their guardian. He tries to live peacefully with them, but eventually his obsession with Banner takes over.
Worthy Opponent: Considers the Hulk this, which is why he constantly pursues him.
Carl "Crusher" Creel was a professional turned ordinary criminal, until he drank a liquid provided by Loki that gave him the power to copy the properties of anything he touches. Creel's intelligence lags far behind his incredible power, leading to his defeat more than once over the years. Originally a Thor villain, but turned into a semi-regular sparring partner for the Hulk, due to his scale of power and simple nature.
Pet the Dog: His personality is virtually identical to that of Zeus, but similarly he had a very well hidden "soft" spot for his favourite son. With that son dead, he doesn't have any nice spots anymore.
Sins of Our Fathers: One of the laws he enforces are to slaughter the entire family of anybody who goes beyond any of his rules in the slightest, regardless if they had nothing to do with it, as it serves as a "more powerful preventative warning".
"You've opened a door to me, Bruce. A crown of light on my face that I never had before. Did you imagine I'd ever let you close it on me? We're going to be gods in this world that's rejected and feared you for so long. We're going to tear it into a billion pieces. I'm the inevitable conclusion. I'm the ultimate - you. I'm the Devil."
An outright malevolent Hulk who represents all of the evil and darkness (and especially the self loathing) within Bruce, the Devil Hulk is imprisoned deep within the mindscape. Appearing as a demonic beast with reptilian traits, the Devil seeks to manifest in the real world so he can turn it into his own personal slaughterhouse, but to do so he requires Bruce to let him out willingly.
What Happened to the Mouse?: Outside of the Chaos War (Brian Banner turned into a hybrid of him and the Guilt Hulk) he hasn't been seen or mentioned in a while, and may have just been an illusion created by Nightmare all along.
Revenge Before Reason: For Gideon, Mess, and Prodigy. Grey has his own motives and Griffin just wants someone to be mad at.
Sibling Rivalry: Grey's real reason for joining the team. He is Glenn Talbot's younger brother. Glenn tormented him during his upbringing, so he is not out for revenge, but to prove himself more capable than his brother by beating the Hulk.
Another villainous personality lurking in the back of the mental plane, this one embodies all of Bruce's guilt, especially that relating to the death of his mother at the hands of his father. Like the Devil Hulk, he is monstrous in appearance (resembling a green Xenomorph) and hellbent on hijacking Bruce's body in order to cause mayhem. After his first attempt (which resulted in the emergence of the Merged/Professor Hulk) failed, he resurfaced years later to try again, empowered by Bruce mourning Betty Ross.
Power of Love: When he realized he was developing feelings for another, he killed her to prevent his powers from going out of his control and threatening the universe.
Sibling Yin-Yang: They couldn't look more different, and have radically opposed personalities as well. They both survived using one of their inherited powersets. He with his Old Power and Skaar by transforming.
Two-Faced: Half of his face was burned off in an incident with Galactus.
Originally associated with the X-Men, but similarly to Absorbing Man, he eventually turned into one of Hulk's regular opponents, due to being one of very few regular supervillains that can actually pose any threat to him.
Once a mentally-handicapped janitor working in a nuclear facility, Samuel Sterns gained green skin, an enlarged head, and the brains of a supergenius after being exposed to gamma radiation. He has fought the Hulk dozens of times, usually as a part of his schemes to Take Over the World
Archenemy: Another major contender for the title, opposing the Hulk continuously and viciously since the Silver Age.
Assimilation Plot: More than once, his goal has been transforming most/all the world's population into gamma beings.
Back from the Dead / Not Quite Dead: He's been killed off more than once, and there's rarely an explanation as to how he's come back. It's even been theorized there's more than one Leader running around from alternate universes.
Charm Person: Can mind control any non-gamma being just by touching them.
The Chessmaster: The Leader always lays out his plans weeks, or months in advance. This is best evidenced during the Red Hulk and Fall of the Hulks storylines.
Do Not Call Me Paul: Hates being called Samuel Sterns. This is somewhat justified; after the Hulk, his gamma transformation likely caused the greatest alteration to his personality, to the point where they may well be two different people, like the Hulk and Banner.
Evil Is Petty: It's been pointed out several times that many of his schemes would have worked... if he chose not to preemptively involve the Hulk, who would have in all likelihood, ignored him. But his petty grudge against the not-so-jolly green giant prevents him from leaving the Hulk out of his plans, thus shooting himself in the foot.
Flowers for Algernon Syndrome: Was fairly far below average intelligence before his accident, so any time he's in danger of losing his powers it's basically this.
My Brain Is Big: And depending upon the artist and how advanced his mental state is, may be exposed. Once when he nearly-lost his intellect and had to get it back, he instead wound up with a thick, gigantic cranium that made it look like he had a giant brain.
In Name Only: In the 2003 video game Hulk(which served as a sequal to the Ang Lee movie), virtually nothing of his character remained from the comics. He was a Stalker with a Crush to Betty, rather than the Hulk, and his obsession with the Hulk (which was rather mild) boiled down to wanting to prove he was stronger. His shape/size changing powers were also left out.
A corrupt, more powerful version of the Hulk from a possible Bad Future where most of humanity was decimated by nuclear war. He built a city with radiation shielding which he named Dystopia, where he rules over the surviving humans like an Emperor.
Future Badass: Believe it or not, he fits this since the extra radiation made him even stronger than the Hulk in the present. For this reason and the fact that because he could anticipate any move his past self could make meant Hulk was no match for him.
Depending on the Writer: Very different assigned origins and motivations, from alien, to angel of mercy, to artificial mutate. One moment she will turn into a giant monster, and the next help a soul to the afterlife. Lamp Shaded in that she has mentioned that she is simply very fickle.
Nice Job Breaking It, Hero: When Hulk destroyed Onslaught's physical form, the entity turned into an incorporeal energy state. Still, all the other heroes of the Marvel Universe combined were helpless before it, whereas Hulk excels at raw power (and not much else), and somehow made it vulnerable to (admittedly contrived) alternative approaches afterwards.
Evil Counterpart: To the Fantastic Four. Oddly, they've never actually fought the Fantastic Four. This was also completely intentional on their part; they got their powers deliberately through the same method as the FF.
Not-So-Harmless Villain: Sure, they don't have much of a street cred, but Vector can repell the magic of Doctor Strange, hurl planets, blast the Hulk into a walking skeleton, and rip apart reality itself. Also, they think nothing of blowing up thousands as long as they get paid.
If one takes time to examine their powers, they're actually considerably more powerful than the Fantastic Four (they were exposed to considerably more cosmic rays). Unfortunately they aren't nearly as smart as the FF, which is probably the main thing holding them back from being major villains.
Possibly the Hulk's most dangerous "adversary", Onslaught and Galaxy Master included. A billions of years old higher-dimensional energy being, and occasional ruler of her own magical universe, fully capable of beating up cosmic entities or rewriting entire realities to suit her whims, and by far exceeding virtually any known arch devils or pantheon godheads in existence. Basically the most evil and powerful woman in the Marvel Universe. She finds the Hulk extremely attractive as a potential trophy husband, due to the upper limits of his raw power, destructive potential, and easily manipulated nature.
Coldblooded Torture: After defeating the Hulk, he let a vulture repeatedly eat his entrails, and sadistically gloated about it. More significantly, he did the same to Prometheus for a far longer time for having the audacity to give mankind fire.
Cruel Mercy: Allows Hercules to rescue the Hulk because he considers simply being the Hulk to be greater than any punishment he could give him.
Date Rape: He has raped quite a few women in the myths. Extra depravity points for forcing himself on them in the form of different animals.
Large and in Charge: Recently drawn this way, being as a big as the Hulk during his fight with him.
Kick the Dog: Hulk offering to make a sacrifice so others could go free prompted Zeus to sum up his actions and say "Wrong religion" and deck him.
Kick the Son of a Bitch: After he temporarily loses his powers, he completely emotionally breaks down due to his extremely pompous nature, is reduced to a hobo living on the streets, and is kicked in the groin and beaten up by Electra when attempting to hit on her.
Kid Sidekick: After his memory is erased temporarily replaces Cho as Hercules's sidekick.
Vetinari Job Security: Pluto, Hera, Apollo and Athena all either replaced or are considered replacements for Zeus as the Lord of Olympus. All are either crazy, completely cold, or at least as evil as Zeus.
Possibly the most powerful known demonic entity, seeking to destroy all of reality, and occasionally used by Doctor Strange as a weapon.
Demon Lords and Archdevils: But unlike other virtually omnipotent demonic entities Zom isn't very clever, and although apparently more powerful as such than any of them, he cannot use it for a lot of versatile purposes.
Physical God: When you require a goddamn MULTIVERSAL JUDGE to stop your rampage, you've more than earned this title.
Sealed Evil in a Can: Up to Eleven. It took the combined efforts of Eternity, Dormammu, and assorted other mystical entities to seal him up. When fighting Hulk the second time it stated that it was only due to Doctor Strange restraining its full power that allowed Hulk to win the first battle, and this was a Hulk angry enough to overcome the full multiversal-scale power of The Sentry. (Hulk later stated that he still held back though.)