I don’t see how death is justice?

I don’t see how death is the punishment for people who commit despicable acts like genocide and torturing people. It seems like when you die, there’s no pain or shame for anything that’s been done so how is that justice?

Just asking out of curiosity because I struggle with injustice. Hearing about the atrocities people suffer through from all over the world makes me ask “God, where are you?!” &
I don’t see how death is consequence of causing so much harm.

I don’t know if I’m even making sense tbh, it’s just hard for me to understand.