As someone who's slightly center-right, a significant number of my opinions are unpopular on this platform. But setting politics and social issues aside, I'd say the nuclear bomb of my unpopular opinions is my belief in determinism - and, by extension, my claim that free will is an illusion.
By that, I mean the idea that you could have done otherwise in a given situation is false. If we had a time machine and could replay a moment exactly as it was, you'd make the same choice every single time. Whatever caused you to make that decision the first time would cause you to do it again - without exception.
A related belief of mine is that the sense of self is also an illusion. To me, these are two sides of the same coin. By “self,” I mean the feeling that there’s a subject behind your face, looking out at the world. But that’s just brain chemistry. There’s no point in the brain where it all comes together - no central “you” making decisions. That’s why there’s no free will either - because there’s nothing making the decisions. They’re simply being made.
The illusion comes from the fact of consciousness. The fact of subjective experience. It feels like something to be you, from the inside. There’s qualia to your existence.