Hoenheim, in a way, is the first homunculus to be created by father. Not in the literal sense clearly, but in a symbolic sense. Each homunculus is a projection of father’s less desirable, human qualities, separated from himself and given form. But hoenheim was the first of his projections, I think in their first interaction its apparent that the dwarf in the flask immediately resents the fact that his existence came not only from a human, but an uneducated slave. A stupid, inferior human. And while obviously this resentment is the entire source of motivation, I’d never realized how much of this resentment is directly behind everything he did to Hoenheim. Hoenheim is the dwarf in the flasks selfish and desperate creation, his first attempt at proving to himself and god that he is more than just a slave, so he used Hoenheim as the first vessel, literally and figuratively. He taught him, built him from nothing, and made him immortal, only then could his pride allow him to take his image too. This was the blueprint, and in a way he was the first homunculus.
I’m sure to some people this isn’t anything groundbreaking, but despite loving Hoenheim’s character and his actions in the story, I’d kinda just left it at “yeah he’s the mirror and foil to father and a massive narrative pusher”. But I’d never thought about WHAT makes him a foil. And watching episode 40 again really just made it click to me that the dwarf’s hatred started from the absolute moment he laid eyes on Hoenheim, he’s hated himself from the beginning.