very few if any xmen use their powers to max ability.
That’s my biggest gripe with the x men world. The pandemonium around them is
when they barely using their powers
unless he wants to lose them, bamfing a limb is a terrible idea
So after 40 years he can’t keep a portal open long enough to stab someone and pull his arm back 
hes a damn good hand to hand fighter, with a rapier being his weapon of choice. one of the best on the xmen
A rapier is all flash
he can teleport behind people as well as hide unseen in peoples shadows. he also teleports to catch most of his opponents off guard. psychics and spider men are really the only ones he cant catch off guard
In most anime’s, people learn on the fly so if they fought before then they should remember his tactics and plan for em
hes already stronger faster and more agile than the average human. how much stronger does he need to be
When you got d list villains throwing cars at people . Knocking out a normal human don’t cut it . It’s like if he fought Juggernaut
he can teleport continentally if he needs be
he doesnt want his fathers legacy. thats not a weakeness
kurt is far, far from the softest xmen. like many, youre confusing kindness for weakness just because hed struggle to kill you doesnt mean he wouldnt bust your ass