Not to disrespect Nube-sensei (totally disrespecting that highlighter yellow alien octopus), but don't stick my GOAT Kawato sensei in that contention. Dude has gone above & beyond of what is possible to bring a hoodlum class into order and most of all train them to become a high-functioning Koshien level baseball team, without knowing a single lick of baseball, just with pure unadulterated wisdom, guts, & unyielding support.
The only one I could consider at his equal level is Onizuka.