There are quite a few weird things that seem inconsistent, but some are just things that readers misinterpreted. One of which is about why the MC let himself be drugged. As stated in the novel, the MC had to let himself be drugged for a while because otherwise, he wouldn't get his 'pain resistance' skill (which never actually showed up in his status). In other words, he would've literally broken from the pain if he didn't get the drugs to distract himself. There are a few other things people misinterpreted but I'm pretty sure that was the biggest one.

The MC is the healing hero, seen as useless and just garbadge in the hero party. He got drugged to obey orders and was basically treated like shit. Someday he regains his personality and manages to turn back time to get his revenge. (All these things are naturally explained in the first few chapters)

I personally loved how he treated Princess Flare - I wonder what her reaction will be once she remembers everything :D

He ends up raping the sword saint "in revenge" for opposing him when, objectively speaking, had every reason to believe he was an awful criminal because every action he had taken in front of her looked shady as shit. Up until that point, he had respected her as one of the few people in the world with proper morals, and in fact she was demonstrating those exact same morals but in a way inconvenient to him. Prior to this, I was all for him treating the ex-princess like shit. She was the primary cause of all the pain he went through, so power to him. Slightly less enthused when he wiped her memory and it turned out that in nature she was actually pretty sweet and it was her upbringing that turned her into an ass yet his view of her remained the same, but I get it, grudges are tough to get past, we still good. Then we get to the bit with the wolf people, where he essentially blackmails an innocent wolf-person (who to be fair, is already a s*ave at that point) with saving her tribe into becoming a disposable piece for him. Yeah, I get it, she was already a s*ave lacking basic human rights, and why not use the situation with her tribe to earn her loyalty, sure. I personally am none too comfortable with him not even acknowledging her as an individual with feelings, but as a disposable weapon, I feel like he could have bought her loyalty with that tribe-saving thing without treating her as a toy/tool, but that's s*avery for ya I guess. I'm uncomfortable but carry on. Then we get to the part I left off at, where he did some shady sh*t to make the Sword Saint think he's a dangerous criminal, and then when confronted he beats and r*pes her. No, I get it, he's a selfish as*hole on a power trip willing to fabricate the reason of "revenge" to punish anyone foolish enough to stand in his way. He's a scummy MC, and this series is a domination fantasy of him conquering and abusing the various heroines. I'll stick to my pu*sy MCs, going on about friendship and kittens and what-have-you... Or at the very least ones who stick to justified vengeance.

An example would be in the bedroom/prison where maids, soldiers, etc r*pes him for level but he explains it's almost pointless as it's much more optimal to do it in the morning (or something) yet after he meets setsuna he explains how it can be done 3 times a day like a meal. He also talks about he will only take revenge if flare is truly "tr*sh" to take the moral high ground but looks forward to taking revenge on the gun/sword hero, even though it was flare who got them to treat him unfairly.

It also doesn't help how he killed the attendants even though he clearly has the ability to remove memories. Also even though kureha has been identified like an "enemy" (like the heroes), it's almost guaranteed that she is going to be spared just so his harem count can be increased (while the heroes will probably die due to them being male).

This is so frustrating... Now that the MC has princess flare and is starting to develop feelings for her, we conveniently find out that her sister is the true "mastermind"... The plot hole being the hero has all the memories, so he should've known by healing flare that she had a scheming sister. But ok, that's even forgivable compared to the hero of the sword being a cross dressing female. Later the MC is going to conveniently point out that he knew all along that the hero of healing is a female and she is going to be added to his harem... WHYUDODIS AUTHOR

he completes most of his vengeance by volume 3 and what happens is he completes some god trials and starts saving people, becomes a father, has wholesome confession time, etc.