So, since someone mentioned Mewtwo, I'll make a case. He's not gonna make top 5 of 5-B, but it's worth a shot.
Aight. So, Mewtwo. Specifically the original series anime + the radio drama. Mewtwo's entire existence is a guinea pig. He was created from the eyelash of a mythical god, the progenitor of all Pokemon (shut up, Arceus). And the person behind it was Mr. Fuji. The scientists were funded by Team Rocket, which as you all know because it's Pokemon, is the Pokemon version of the mafia/yakuza. To them, it was the project to create a warrior god, but to Fuji, it was an attempt to master cloning. As Fuji earlier lost his daughter, Amber, and Mewtwo could give him the secrets to bring her back. He works day and night on this, never coming home, until his wife can't take it anymore and leaves him, which causes him to further delve into his research.
Now to Mewtwo's perspective. They started his creation, and Mewtwo is gestating in a lab vat. In his first moments of life, he telepathically connects with the AmberTwo, the consciousness of Amber. They become fast friends, and Mewtwo also gains the friends of some other Pokemon clones, that being clones of the original 3 starters. All is going well until one by one, the clones start dying. The cloning process isn't perfect, and their consciousnesses can't last more than a short period of time, Mewtwo being an exception because he's a physical god. AmberTwo is the last one to go, and as she's fading, she tells Mewtwo that life is beautiful, and he should be happy that he's alive. And with that, she dies. Needless to say, Mewtwo doesn't take this well, because he's not even a week old at this point. His has a psychic "tantrum" and the only thing the scientists could do was put a bullet in his head. Mewtwo dies but regenerates, and the scientists wipe his memory, but the seeds of the event still weighs on his unconscious mind. Meanwhile, Mr. Fuji gives up on bringing his daughter back, his only goal bringing Mewtwo into fruition.
Years pass, and Mewtwo is fully realized. He asks who he is, and they tell him he's Mewtwo. The scientists celebrate his creation, and talk about all the tests they're going to run on him. This is when Mewtwo realizes that these humans don't care for him as anything more than a guinea pig, and they don't care whether or not he's alive. His response? He blows up the lab bit by bit before nuking the island altogether and leaving.
On his travels, he runs into Giovanni, who tells him he can help Mewtwo control his power. Mewtwo, as remember he's been conscious for like a day at this point, believes Giovanni. Giovanni puts armor on Mewtwo and has Mewtwo do...tasks for him, but unbeknownst to Mewtwo, Giovanni is having Mewtwo commit crimes like stealing Pokemon by the hundreds. When Mewtwo catches on, Giovanni gloats that Mewtwo was nothing more than a weapon to him. This completely disillusions Mewtwo about humans, and furthers his doubt to whether he's even alive, and what he's meant to do. Mewtwo's entire journey is his existential crisis.
Fast forward to the events of the first movie. Mewtwo controls an island and tricks the greatest Pokemon trainers (so far) onto the island for training, and when he reveals himself, he clones all the Pokemon there so he can pit them against each other, as validation for if clones are worth living. Mew, his "parent", shows up, and in the Japanese version, Mew takes the opposite approach. Clones are abominations that should be put down. The American one nixes this. And then they fight. The difference between this and the other Pokemon battles that everyone seems to forget about is that this isn't for sport, but to the death. And nobody would come out on top, so Ash runs in the middle of a clash between Mew and Mewtwo, which kills him, albeit temporarily. This is when Mewtwo realizes. A young boy, a Human, sacrifices himself for the sake of all Pokemon, whether or not they were clones.
The circumstances of one's birth are irrelevant. It's what you do with the gift of life that determines who you are.
From here on out, Mewtwo has a change of heart. He takes his clones and flies off, wiping the memories of all involved and sending them back in time. The next time we see Mewtwo, he's caring for his clones, and even saves the lives of humans if they're in danger when he's present. He saved Ash's bus when it was about to go off a cliff. And he's even willing to sacrifice himself for his fellow clones. And even when Team Rocket tries to take him and his clones, he doesn't hate all humans again. After the events of the Mewtwo Returns special, we don't see that Mewtwo again, sadly. We get a shitty version in the Genesect movie that's not the same.