In reality, even my title is redundant. How many times have you stumbled onto a good villain?
Let's step back and evaluate this stereotypical character—the villain. They exist to confound the protagonist, the hero(ine).
Never once does an antagonist think they are evil or bad. They consider themselves, for the most part, just like everyone else. They exist to have what they want. The catch is simple—they're not suppose to have it. THAT is what makes them a villain.
Take the "evil" queen in Snow White. For my purposes, we'll use the children's fairy tale. Sure, she dabbled in the black arts and wanted Snow White killed. But, in her defense, it was only to get rid of the competition. Yes, a little drastic, but the queen only saw Snow White as somebody who was about to usurp her position as the most beautiful in the kingdom. You tell me, what beauty queen wouldn't kill to keep the title?
But, I digress. Never once did the evil queen think of herself as bad, the villain or even evil.
In your next work, think about the antagonist in a different light. Don't attempt to describe your villain as evil incarnate, or so vile that black paled beside him/her.
With that said, there are times when evil is just plain bad. Demons, Satan and such creatures. But, even Satan doesn't think of himself as evil. In fact, according to stories, he warred with God to take control. Who hasn't done that? In today's world we have winners and losers. That's just the way it is. Satan lost but I don't think he ever really saw himself as a bad person. Even when Satan lured Eve with the apple, he was trying to help her to see things as God saw them. Yeah, it was a con job.
There are those "creatures" who perform bad deeds. Yes, you could consider them evil. They probably don't see themselves as bad but just getting the job done. Just like thugs who crack kneecaps for a living—it's all in a day's work. Yes, they probably know it's not the proper thing to do but they have a job to perform.
Consider this. If an entity is born out of the clouds of heaven, is s/he immediately considered good? Do angels sing at every footstep of this entity? Do they go around stating how wonderful, good, perfect they are? The same applies to the entity spawned out of the depths of hell. That entity doesn't trudge around stating how bad they are. Do they rub their hands in a ball and let out a maniacal laugh? Maybe they do but that's part of the stereotypical job description YOU'VE given them.
In the future, never have your villain think they are the vilest creature or they are performing the evilest deed. They're just average Joe doing what they need to do—confounding the hero(ine). Even the good guys, the hero(ine)s do bad things, so a villain is just doing bad things with better flair. SHOW how evil they are, don't bother telling us with fancy descriptive words like "vile," "evil," "bad," "disgusting," "wicked," "malevolent," "despicable," "abominable," or "malicious." As they say—Action speaks louder than words. SHOW us the action. Show us the villain.