Probably Bill Cipher, he's sadistic as heck and openly enjoys being evil.

Probably Palpatine. Guy is one of the most evil villains I have ever seen in cinematic history

Well, in Legends, it seems like Palpatine sees himself as a good person.

Although he can't really communicate his emotions, I feel like all the Ghidorahs approved as PE would take it as a compliment.

Palpatine

Joker, Carnage, and many other card-carrying villains.

And Frieza

Scar, General Grievous, Black Manta, Jill Roberts and Slade.

Contagion probably

Zhan Tiri.