Source: comicbookglobal.com

4. Dormammu

If you checked out Doctor Strange last November, you're already familiar with the dreaded Dormammu, the ultimate of Doctor Strange's foes.

Dormie lived in the Dark Dimension, a dimension as without light as it was without creative naming. There, he had a fleet of minions known as the Mindless Ones. They were not too bright. Really, whatsoever.

After briefly dealing with Captain America during World War II, Dormammu found a true foe in Doctor Stephen Strange, the newest Sorcerer Supreme. They battled numerous times, with Strange always coming out the victor. Later on, Loki and Dormie tried to pit the Avengers and Defenders against each other, but it failed. A later, smaller-scale attempt to make Ghost Rider and Doctor Strange fight failed in kind.

He possessed Strange for a bit, and then tried to lead a Mindless One invasion of New York City, but Spider-Man stopped it. Poor Dor-mumu. Never gonna succeed at taking over the earth.