Butthurt basically means "You tried/did something stupid, and now you are unreasonably upset because you didn't consider the consequences". Much like anyone whose has ever tried unprepared anal sex finds out it hurts, or for a more pleasant example, how a child gets spanked for misbehaving. To use in a video game context, you could say "You knew I'd uppercut every time you jumped at me, but you kept doing it anyway. Stop being so butthurt".
As far as I know, I don't think anyone uses the term in a "lol rape" sort of way.
As far as I know, I don't think anyone uses the term in a "lol rape" sort of way.