Damion Poitier played the Mad Titan first, using much of the same motion capture technology used later. As such, his first official appearance in the MCU wasnt quite the Thanos audiences got later.

Cull Obsidian is the bruiser of Thanos' (Josh Brolin ... like character is unrecognizable next to Terry Notary, the motion capture actor and stunt-double extraordinaire who plays the part.