Ebony Maw
Ebony Maw is one of Thanos' most loyal servants. This scary-looking alien is incredibly smart and manipulative and can teleport and generate forcefields. He also almost killed Doctor Strange in Infinity War.
Tom Vaughan-Lawlor is the actor responsible for bringing this character to life and, to be honest, they look nothing alike. The CGI work on this one is incredible, and you can't even see Vaughan's features anywhere in Maw's face.
Proxima Midnight
Since we just talked about Ebony Maw, let's mention another one of Thanos' goons: Proxima Midnight. This Black Order member is extremely strong and fast. She carries a spear and is pretty scary to be honest.
Proxima Midnight was brought to life by two actresses. Carrie Coon voiced her in Infinity War, while Monique Ganderton was the one whose face and body were used. In End Game only Ganderton participated because the character does not speak in that movie.
Talos
OK, before you tell us that Talos is not a villain - yes, we are aware that he is actually good. For a good part of the Captain Marvel movie, we are led to believe that Talos is evil but in reality he was just protecting his people all along.
The makeup and CGI on this character, however, basically forced us to include him in this list. Who would've thought that the handsome Ben Mendelsohn was actually under those green prosthetics?