Thaddeus Sivana didn’t start as a bad guy. He wasn’t one of those people to blame his childhood for growing up to be a bad guy (but one could say that was a big part of it), he blamed it on being told by a man he had met only once that he would never be good enough.
A man who claimed to be the most powerful in the universe told he wasn’t good enough. Combined with the constant sneering from his father, Thaddeus was ready to prove all of them wrong.
He worked hard only to be proven wrong.