Most shows with super villains leave me wondering why they just randomly want to destroy humans, but the Infinity War/Endgame movies gave a reason.
Apparently, in the comics, Thanos wants to wipe out half of all life because he has a romantic crush on "Death" and wants to impress her.
Thanos was convinced his evil was for the greater good, and plenty of people might even agree with him, in theory. I liked knowing his motivation wasn't simply that he hated humankind for some obscure reason or no reason at all.
Some people think the best movie villains are ones you can look at and actually agree with their point (at least on some level).
Black Panther was similar.... the main antagonist was one who thought Wakanda should be doing more to help the disadvantaged. (Which he sort of had a point.)