I'm not so sure. He did threaten to kill everyone on Earth during the events of "Ends of the Earth" for the self-aggrandizement of his ego. He also wanted to give a person HIV so he can cure them, once again for the self-aggrandizement of his ego. Otto could indeed be genocidal if he felt it was in his best interest, I think he might even do so today if he felt it served a greater purpose like protecting the world. Unlike Peter, he has no qualms about playing dirty when need be and I love him for that.