This is pretty bad, main character seems comically evil, killing allies not for any good reason but just because the author feels the need to make him seem evil. In a setting where people also have multiple lives he doesn't even try to pretend these murders are accidents or that he has some excuse to do so, he just does it straight up and "hopes" that his victim is on their last life. Sometimes they aren't and those people are now out there fully aware of his character. Haven't read far enough to see if this has any consequence yet but he's a fairly famous character and no one has pointed it out yet so it's quite doubtful it will.
Main character also repeatedly does some very stupid things for no reason(ex. When pretending to not have active skills, he decides to use active skill in a battle that he is not struggling in for no reason, and has to make some stupid excuse and everyone believes it), it gets acknowledged as a very stupid blunder, and then everyone moves on like nothing happened.
A lot of deus ex machina, pulling out new skills or items he never had, or a particularly egregious one where he trips during a duel and defeats a far superior enemy because he just happened to fall down in the right way.
Internal inconsistency is also present, or a mistranslation. One character is surprised that someone is affected by poison, and has an internal monologue about how there aren't any monsters that use poison in the dungeon, complete with an image of a 4 headed hydra that they were in the middle of fighting against. That hydra controls 4 elements, specializing in ice, fire, wind, and poison. I'm not sure if that's a mis translation or what but holy crap. If I didn't know any better I'd assume the artist is doing this on purpose to troll the source material author on his internal inconsistencies.