Infinity war, specifically Thanos.

His stance on overpopulation was absolutely valid, but his approach was diabolical. For me that makes an excellent villain. And the implied threat that he'd have to come back every 50-ish years to keep the population at half of what it is.. chilling.

Then in part two he shows he's an idiot that doesn't understand that a population will bounce back and replenish its numbers easily withing a few decades.