So here's my take on villains in d&d. My best villains have always been built on one of two ideas: "even assholes love somebody/something," and, "personal ambition over community."

Those two aspects have made for some REAL dynamic villains and great foils for my players

Especially if you take either to an extreme. The first campaign I ran, main villain was so heartbroken over the loss of his wife he went about trying to find a way to kill the goddess of death for "taking" his wife from him.

Minor villains were an anti-party wherein the paladin only stuck around because he was hopelessly gay for the party leader who was super cursed

In my more recent campaign. Party dropped a skyship on a pirate who kidnapped the bard's cousin. They stole his journal. Then after almost killing him they found out hes married. Still an asshole, still terrible, still allowed to think his wife is the most beautiful woman ever.

That journal revelation resulted in the party going to SAVE that asshole. Totally different outcome than expected, but still the same end point: they talked instead of fighting and there's a good chance that pirate won't be a villain anymore.

Now mechanically, conflict resolution through de-escalation isn't really supported in RAW D&D5e. But the minute you show your villains as extremes of similar characteristics to your party, the WAY players will want to interact with them will change.

This also goes for making villains that are just... Pure evil. The ambition over community villain is the best example. The party encountered a business man who profits off of downing skyships. They asked him if he thinks he's a better person now after a chat

That one, while maybe not a full villain in classic terms, still said no because they view themselves as terrible but not knowing how to be anything besides terrible.

Then cue the world domination villains. The "I want x thing so bad I'll do anything to get it" types. That's ambition over community at the highest point. Make them lose their own identity to their ambition and you have a villain that is terrifying

Mainly because they've lost themselves to their ambition the way some heroes start to lose their identity outside of being a hero.

Anyways. Just some thoughts on degrees of villainy and the two questions I try and answer for mine