Unambiguously powerful and infinitely wise, teachers in comic books come in all shapes and sizes. Honestly, they tend to have too much power, and that's why they're - mostly - destined to perish at some point. Mentor figures in Marvel Comics have it no better than the teachers of the DCEU. They show up, they pass on their powers and knowledge, and then they hit the proverbial road.
Who's the most powerful, though? If Odin had to take on the Ancient One, or Splinter went toe-to-paw with Henri Ducard, who would come out on top? These people spent their lifetimes training others - but how would they themselves fare against others on their level?