Johns teacher would probs best be iceman as he is the one most similar to John in terms of his powers work?

Johns fatalities

His hand becomes a large spike through the opponents face

He makes an earthen tomb which crushes the enemy into mush

cant think of a third lol

As for Jax, I think Wolverine would be best

he would only have one fatality and that would be to rip an arm or leg off then use that to smack the foes head off :P