To everyone harping around Stark abs-of-steel:
a) First of all, he
knew where demon gothic loli would aim for. He literally says so ... and it actually makes sense; sure, aiming for the head is the best bet, but he raised is axe, so he could block a attack to the head. The second best option is on the abdomen, where a lot of vitals are with no bones to protect them, so she went there. In other words, he actually guided her to attack there
( yeah, Stark can plan out stuff. Who knew?
)
b) In this universe you can use mana to block physical attacks. We already seen Frieren doing that and, if you read between the lines, Frieren hints that Stark strenght is not all about muscles. I assume that Stark just used unconsiously a self-learnt ( and less effective, since he bled ) version of the technique Frieren used to not lose her head in jail when that hotblooded demon tried to decapitate her..
In resume, he used the enemy knowledge of human anatomy to guide her attack to a obvious weak spot and used mana to soften the blow in a very specific area of the body. Nothing that we haven't saw already in universe, but seeing Stark being able to pull out that in his feet after a beating is still impressive anyway ...