Gotham's rogues are some of the weirdest, grossest and often most unpredictable supervillains in existence. There's a reason rent is dirt cheap in the city, and that's because at any moment your humble abode could be ravaged by Poison Ivy's plants or frozen into a block of perma-ice by Mr. Freeze - with or without you inside.
But not all villains were created equal. While most would flee in horror from the Clown Prince of Crime, they'd probably yawn and continue to order breakfast if the Carpenter came in to try and rob a store.
That said, plenty ne’erdowells get reputations that don't reflect how dangerous they actually are. The Riddler is a dangerous Saw-trap master, yet is generally about as imposing to people as a Junior Jumble. Mr. Freeze is regarded as a cold-hearted master criminal who'd rather freeze you to death than speak to you, and yet you could probably "defeat" him by asking him whether he's doing alright in a genuine tone of voice.
Perception is a tricky thing, and it's only made trickier when the people you're trying to judge are all costumed criminals who want to be the next Satan.
He's... literally called Nobody. That's a name he gave himself.
And honestly, he was right. Maybe don't get murdered by a child next time.