the most strict mentor in comics, Japanese or American?

what comes to my mind relating to this question:

America: Tie between Batman and Deathstroke

Japan: Piccolo

Do you have ideas?

Piccolo is pretty scary lol. Literally did nothing but beat up and abandon Gohan in most dangerous places imaginable lol.

Another one that comes to mind is Vice Admiral Garp. He really loves Punching people over absolutely nothing. And these aren't kiddie punches either.

Maybe Levi from SNK if you consider him a mentor. I mean he can be ruthless. especially latter in Manga.

From Comics i would probably say Batman.