Comment by Nelson Mandela on Tired27

@Nelson Mandela how about you actually look at this chapter.
There was no explosion with his punch, his first punch using explosion destructive wave, despite having explosion in the name nothing exploded and against the enemy it did no damage and only pushed him away.

And 10x you just made the fu** up so how about you use actual facts from the manga rather than your own head cannon.

Using promote level 3 the MC can't maintain for very long but it's the same for promote level 1 and 2.
Promote uses demonic qi which is harmful to humans in this universe so no matter what level he uses, promote puts him on a time limit. All you have to do is read the previous chapter, bro was writhing in pain just by using the demonic qi from promote level 1 and would have died if the priestess never used divine power to allow his body to accept it.

Using a lower level promote still activates the demonic qi which is what puts him on a time limit so he can't stall and he still wouldn't be strong enough to stall.
Promote level 3 without combat arts did essentially no damage which would indicate a lower level promote with combat arts wouldn't be effective either.

Yeah the barrier isn't permanent but what would last longer, the Barrier or the MC?
Reidruun is being stalled by the blonde knight, gluttony has left for a while and the Dark Elf can't break the barrier so they're not going to arrive to help any time soon.

Plus the whole goal isn't to kill the MC but the priestess. Can he defend himself while defending the priestess long enough against a much stronger opponent without promote level 3? Highly unlikely.

The MC decided to go full power in order to end the fight quickly as that gives him the best chances of victory as the main goal is to protect the priestess.