You really need to go back and read the early Supreme. He was like Larsen said Superman being a dick, with a real bad attitude and possibly little regard for supervillain life. If they opposed him, and they had to die. They died. It wasn't the Plutonian, because he didn't snap, but he had major attitude.
I also have the feeling that Larsen is a little vague about his Supreme's character and direction, and wish he wasn't so adamant about avoiding Moore's version, which I enjoyed. The Supreme of the first 40 issues, in my opinion, was unnecessarily hyperviolent, and so intensely focused on being a mean-spirited, selfish jerk that it defined his character. He became boring; I knew he would never change or develop. Reading about him offered no surprises, and certainly no joy. I hope Erik Larsen quickly decides that depicting dickery isn't entertaining, engaging, or amusing. At least, I don't think so.