Thanos — Josh Brolin
In 2012, Damion Poitier got to play Thanos in The Avengers. However, Josh Brolin went on to replace the stuntman in the four movies that have since come out. If you were impressed by how realistic the character looked, you should know that they used computer technology to bring him to life. How awesome is this?
Kaecilius — Mads Mikkelsen
In 2016, Mads Mikkelsen was enjoying the peak of his career. Not only did the Danish actor star in a TV show called Hannibal, but he also appeared in Rogue One: A Star Wars Story and Doctor Strange. He played Kaecilius in the latter. The actor had to spend hours in the makeup chair as the artists worked on making this gray and purple mask effect. All that effort was definitely worth it!