Because of Avengers: Endgame’s time-travel element, fans get to see two different versions of different Marvel characters, including two different versions of the Mad Titan Thanos (Josh Brolin).
In the original timeline, the old Thanos is found in retirement in a farming planet. He uses the Infinity Gauntlet for the very last time to destroy the stones, sealing the deal on The Decimation that he had caused in Avengers: Infinity War. Traveling back in time to obtain the stones and undo the Snappening, the Avengers run across a younger Mad Titan from the year 2014. Somehow, this Thanos manages to jump forward in time from his dimension, the one Iron Man (Robert Downey Jr.), Captain America (Chris Evans) and the rest of the Avengers are currently trying to fix.
To keep track of the two different Mad Titans, the creative team behind Endgame decided to give younger Thanos a nickname, dubbing him as the “Warrior Thanos.” Speaking in an interview with Empire Magazine, Endgame co-director Anthony Russo explains the nickname that the team decided to give the character.
"We refer to him as Warrior Thanos, the version of the character before he put down his armor and became enlightened and wanted to search for the stones," Anthony Russo said, "He's angrier; it might be his flaw in the film, that he's a little bit more precocious and self-confident, not quite as enlightened."
The younger and older Thanos might have the same facial structure, however, “Warrior Thanos” is a slightly different character. Not only is he far more agile, but he’s at the peak of his physical prowess. Imagine that. The older Thanos beat down the Hulk (Mark Ruffalo) in Infinity War. What would the younger Thanos have been able to do.
Avengers: Endgame is currently screening in cinemas.