User blog comment:Looperreallyreallysucks/Pure Evil Discussion - Avengers: Endgame/@comment-25075214-20190508232420

Well, it would be obvious to believe that the 2014 Thanos would've become Pure Evil. Sure, the original Thanos did show remorse for killing Gamora and mistreating Nebula before he died. But when his 2014 self learned about it, along with the fact that the Avengers are close to undoing his actions through time travel and that everyone else will not appreciate his actions for the universe, he abandoned his beliefs of balance and became more depraved to the point that he plans to destroy the universe and recreate it in his own image. He lost whatever respect his future self had (especially towards Iron Man, Thor and Captain America) by calling them "unruly wretches" and gloated to them that he would enjoy destroying the Earth out of spite against them for ruining his plans. He also didn't care if the imminent catacylsm would've killed his daughters as well (especially the 2014 Gamora and the present day Nebula); even when Nebula tried to convince her 2014 counterpart to sever all ties with the 2014 Thanos, the 2014 Nebula refuses by saying that he wouldn't let her, implying that she still fears him due to his low tolerance for failure. Not to mention that losing his planet to overpopulation doesn't excuse his next plot of wiping out all life in the universe and recreating it under his own image.

Personally, I would consider that enough to qualify him as Pure Evil, but he did came from a different timeline.