Many many words are better than "evil". How about "autocratic" or "dictatorial" or "power-hungry" or "delusional". Or perhaps a phrase like "ruthlessly uncompromising". All of them convey much more actual information and still have your judgemental tone.

For what its worth, I think "evil" is a word that shouldn't be used outside of storybooks. It is a binary word that is far too overgeneralised to the point it is meaningless to ascribe. It doesn't serve any persuasive or descriptive purpose.