Avengers: Infinity War

[Cheesegear]

Delusional? Sure...

That's the problem.
In the comics, Thanos had to murder a whole bunch of people, 'cause then he could get into Death's pants. There was a purpose to it.
In the movies, Thanos seems to be murdering a whole bunch of people, because he can, and his goal, is simply delusional, given his reasoning, and unlimited power. Given unlimited power, you choose to destroy half the universe? ...What are you, 14? Did you put any amount of thought into how unlimited power could be used for literally anything else, literally?

Which is the same problem that Ultron had. When your motivation doesn't make sense, you lose credibility, as a villain.
...Unless you're in a movie designed to sell toys to children, in which case nothing matters, and you can do whatever you want, no matter how stupid it is, because 'it's a movie designed to sell toys to children', so anything, is good enough.