Evil is such a simplistic way to describe any character, be it Iago or Caliban, or any character from history.
A character I would love to play is Iago, from Othello.
Thou dost conspire against thy friend, Iago, If thou but think'st him wronged, and mak'st his ear A stranger to thy thoughts.
Macbeth's self-justifications were feeble - and his conscience devoured him. Yes, even Iago was a little lamb too. The imagination and the spiritual strength of Shakespeare's evildoers stopped short at a dozen corpses. Because they had no ideology.
What makes Iago evil? Some people ask. I never ask.
There’s an Iago and a Romeo within all of us. There is that lover, and there is that sociopath.