Was he reprogrammed for good or something? Didn't he rightly determine that humans were the cause of all the bad things in the world?
I don't get how is was "approved" to be a hero.
Venom and Green Goblin both went "suicide squad" with bombs implanted to serve SHIELD, but also had acts of heroism. Venom known as the Lethal Protector and Goblin having his own charade.
Magneto, obviously wanting to kill humans and make mutants reign supreme, on many occasions attempted to follow xavier's dream most noticeably after he died.
Juggernaut has fought on the side of good when his god deems who his enemies should be, his main hatred was for Xavier but when it comes to things like the planet being in danger, he's been a good guy.
Black Cat was a thief, but with Spider-man she had her own times when she was a good cat and actually fought crime with Spidey. If it wern't for inferior spidey oct, she may have stayed good.
But then we have Ultron, I don't recall anywhere where he was a good guy other than the very very earliest incarnation of him when Hank designed him.