Zeus was promiscuous rather than rapist. Kind of most popular guy on campus whom all the girls want and who makes their dreams come true. Puritan ethics can condemn his serial spousal infidelity, but he was not rapist per se.
Underworld was not hell in a Christian meaning, people were not sent there as punishment for sins or such. However, it was not a happy place where people go after death. No one wanted to go there, and no one wanted to talk about it or its lord either.
I think underworld was a metaphor for real world or slavery. People will fall into that condition if they lose social status and become an underclass in a Greek society, like if their city was destroyed by enemies. Hades ruling over that probably meant he was like a slave trader or something. The kind of Geoffrey Epstein type of figure.
Do not know much about Poseidon, but he was likely a low-key Zeus who had his fun but did not overindulge himself like Zeus who tried to stick it into every pussy out there. Poseidon had taste and only fucked girls (nymphs) he liked.
