In many respects, Paradise Lost is a sort of revenge tragedy. Adam and Eve are the innocent victims of Satan's attempts to seek revenge against God. He sort of feels bad about it – he even cries when he sees Adam and Eve – but then he realizes he must continue with his plan. In the long run, Adam and Eve will win out, but in the poem nobody really wins.
Satan is incredibly complicated, not least because at one point he almost doesn't go through with his revenge because he's so moved by the sight of Adam and Eve.
Satan is delusional for thinking that it is at all possible to get revenge on God; God, after all, cannot be defeated.