I didn't like the MC because of some major red flags from the very start.

[SPOILER]He's overpowered but he didn't intervene and save the knights who were fighting that demon that attacked town. He just used ti to level his skills... which he could easily have done outside of that battle. Even after the demon was wounded he didn't finish it (some bullshit excuse about coming from a world where people don't like killing), and it went on to kill more innocent people. Then he had no qualms about slaughtering his way through a dungeon shortly after.

He ignored that chained slave going by who looked she was hoping for his help, when, again, he's so overpowered that nobody can stand up to him -- especially knowing the levels of everyone present. It wasn't so much that he didn't do anything (which is understandable because of laws) as the fact that he just didn't want to get involved, which shows that he's not going to be the kind of proactive main character I want to read about.[/SPOILER]

There were a few others things and by the end of it I just got so sick of him that I didn't care to read on. Too many good stories out there for me to waste my time on the type of MC I can stand. He has no interest in helping anyone but himself, and he's just going to keep making annoying decisions over and over, because it was clear by that's the kind of MC he is (I got to the end of the dugeon he gets pulled into with the slave girls).

I really hate people like that and I don't want torture myself by following one around and watching him make retarded decisions at crucial moments of the plot... so unless he changed (which I don't see happening) then I think it's just that you probably have a better stomach for characters like him than I do.