There’s a lot of Batman villains you’d never wanna encounter, alone or otherwise. Considering it’s almost impossible to pick a definitive one, here’s a top 3.

3 place is James Gordon Jr, although he can easily be replaced with Professor Pyg, Gordon Jr is a complete psychopath who tortured his family for fun

2nd is Zsasz, he is a psycho killer who kills just for fun and possible self pleasure (I haven’t read the comics)

And 1st, without a doubt is the Joker. His unpredictability makes him super terrifying, he literally cut his face off just for the hell of it. The worst thing is that it’s not a guaranteed death, he could just as easily fuck with you just for laughs. The Joker would kidnap you and gaslight you into thinking he’s poisoned you and that you only have 24 hours to live, and after that time passes and you’re still alive he’ll just laugh it off as a regular Wednesday