I've read it in almost a single go, is not that it have a couple ass pulls, is a costant, everytime MC is in a fight he is the weak part, then he gets the boost needed to win, is not a weird cliche in battle stories, but here is always the same turnaround and it never changes.
And yes, the last chapter is dissapointing, it just ends, manga are better there to show the important characters life after everything gone down, here we see MC, dad, gf and 2 monsters.