They're not heroes. These guys are monsters and have done monstrous things in the name of saving people, but it was about their own selfish need for them and not the greater good. However, Stefan and Damon were clearly trying to be better. Damon in s8 mostly. Stefan struggling with doing to right thing and following a moral code for the entire series. Katherine was always about protecting herself and her own self interests. The only real difference between them all was that Damon and Stefan had other people they were willing to die for. Katherine was only about herself.