Turning Good Characters into Villains

Fellow r/DnD/ patrons, I come to you for help. I am currently working on a campaign that a few buddies of mine will be playing. The basic gist of it is that the players will be henchmen-in-training for a stereotypical Sauron-type Overlord, but in a more comedic style (the Overlord is a family man with a loving wife and a couple of children, some grown, some kids). Now here's the kicker, and where I'd appreciate some input: I need to make the "heroes" who oppose the Overlord be the nastiest villains I can while still being good or good-leaning neutral. This is in 5E to be precise. So far, I've already got a paladin that is basically Hitler toward monstrous races (a good 80% of the Overlord's subjects), a wizard that just treats monsters and evil races as lab subjects, a sadistic ranger that likes to torture monsters (kind of inspired by the douche from Goblins, but less of a pervert, just a sadist) and a holier-than-thou priestess I plan on having captured and corrupted into the service of the dark gods. I need other ways of making stereotypically good characters look evil, so basically flipping the alignment schema. Each of these heroes, as well as a few still in development have their own small kingdoms bordering the "evil empire" that the players will be infiltrating, laying siege to, etc. So, think you can help me make the good guys look worse than the bad guys?