Villains whose entire philosophy falls apart under the slightest scrutiny

Thanos - Avengers: Infinity War. It's almost redundant at this point to repeat what's been pointed out times beyond counting by others, but his plan to prevent overpopulation by wiping out half of all life in the universe flies in the face of everything we know about how population growth dynamics and consumption of resources work. Not to mention he could easily use the power of the six infinity stones to simply make more resources. At the end of the day, he's not a savior, but a stubborn fool that can't admit his plan to save his home planet wouldn't have solved anything.

Terence Fletcher - Whiplash. He justifies the horrific bullying he inflicts upon his students as being necessary to motivate the next great musician, citing the story about Charlie Parker being humiliated by Jo Jones. Firstly, that is not at all how the incident went. Secondly, there's a huge middle ground between tolerating mediocrity and vicious aggression towards anything less than perfection. The possibility that stern but fair mentoring with equal application of criticism and encouragement could be a valid teaching method that would encourage the decently talented and exceptional students alike is utterly alien to him.

Andrew Ryan - BioShock. Wants to create a utopia in which the most talented individuals of the world could flourish without the restrictions of government, religion or any oversight whatsoever. But a utopia of geniuses, creators and artists doesn't just run itself. It seems that he legitimately did not consider that a working class, which he looks down upon and calls "parasites" because he thinks laziness and failure are the only possible ways anyone could be poor, is vital to perform the menial tasks that the individuals in his 'Great Chain' don't want to do. By the time you arrive there, Rapture is falling apart under a civil war, and Ryan is blaming everyone but himself.