I honestly would like a villain that's a former Dragon Warrior. Like a sealed villain is freed and the big twist is that he's one of Po's predecessors. I also like the idea of such a character having a really good motive for going down a dark path like after vowing to protect the innocent he discovered those he protected were capable of evil acts just like those he had been protecting them from and was so disgusted that he turned away from his vows instead trying to destroy civilization so that it could be rebuilt. I just think that'd be interesting to see especially if the villain was actually a nice guy Po could get along with but for them to have such a massive divide that there can be no peaceful resolution. I also like the idea of Po seeing corruption firsthand and beginning to have doubts as well.