Okay...like I've said before I haven't actually read many Marvel comics so I don't know all the villains in the Marvel Universe. So I'll go with villains we've seen in the MCU so far.
Narrowing it down to two villains (since I can't pick just one) Here we go.
Loki is a most definite on my list of favorite villains. And I really love Tom's portrayal of his character.
And last but not least, Wilson Fisk (aka: Kingpin) from the Daredevil series. I really liked Vincent D'Onofrio's take on Wilson Fisk's character was really great.
Alright! So as always, feel free to leave a comment if you want!