Bruce Banner

General Thaddeus Ross commissioned the gamma experiment, ostensibly a radiation-resistance study, actually an attempt to recreate the super-soldier serum. Banner spends five years on the run afterwards.

Brought in to trace the Tesseract's gamma signature, not to fight. He loses control on the helicarrier, and comes back on his own terms for New York.

He flies a Quinjet into deep space to remove himself as a threat and crashes on Sakaar, where he spends two years as a gladiator. He is Hulk continuously for that entire period — long enough to develop speech, preferences and an ego. He misses the Sokovia Accords completely.

Thor is stranded on the junk planet Sakaar, ruled by the Grandmaster, where he's forced to fight Hulk, who has been there two years as a gladiator. He didn't capture Hulk; Hulk crashed there, was found, and became reigning champion, which the Grandmaster adores. Hulk isn't controlling himself, and nobody else is controlling him either.

"Smart Hulk" is permanent and deliberate: big and green, in glasses and a cardigan, with Banner's voice, vocabulary and personality entirely. He achieved it on purpose between films.

Gamma radiation gives him the best survival odds. It permanently damages his right arm. He explicitly wills the returned to reappear exactly where they vanished from, in 2023, having experienced no time at all.

Established in She-Hulk, alongside his cousin Jennifer Walters gaining his powers without the rage. Skaar has not been followed up on.

The Punisher (Jon Bernthal) and Hulk appear. On Hulk: I also don't have reliable detail on what state the character is in here.