Multiple Dragon-class mysterious beings, together, were pretty much afraid to even attack him.
Dude is terrifying. It's like, his every moment and word scream, "It doesn't matter how strong you think you are, I'm going to mess you up if you cross me."
He's technically only the #7 in the S-class, but that's mostly due to his lone-wolf nature. Even #2, the psychic Tatsumaki, pretty much only respects him out of the entire S-class, and he's often called the most powerful human in the world.