Ah, I reread the first chapter and remembered why I dropped it on the first chapter the last time I read it.
I respect the guy for putting his foot down and leaving a bad relationship. It may not be the best way to handle it, but it does sound like even at the best of times the girl was a bit overbearing. Like the whole "we should not measure our magic power because swordsmen don't need it", just because she was a natural with the sword. And again, he could have handled things better, but a lot of people don't. And reasonable people leading a healthy relationship and making sensible choices makes for a poor story. I'd rather he left than seeing him be stepped all over.
What made this disgusting to me, however, is how he disappeared and how everything immediately went his way. First his sudden disappearance. It's completely unnecessary. As he said, he had been working as an adventurer on his own and did well and earned a fair amount. He doesn't seem to have a bad reputation with other people, the abuse is a private thing and only from her. So why is he so eager to drop everything? Also, this means this guy had no life outside of his relationship to this girl. No friends, no family, nothing. He can drop off the face of the world with no regrets. That's a terrible main character.
And then the ridiculous contrivances. Just a haircut and he is super hot. He walks into a new guild and his magic power that he never trained or knows anything about is so far out of the norm that it can't even be measured. Then immediately a cute, powerful girl gets all horny for him while manually measuring his power. And also his ex immediately regrets her behavior and wants him back before he even finished dumping her.
Any single one of those might get a pass as a way of showing him leaving his past behind, exploring a new facet of his personality, telling us which way the story is heading, etc. But dumping everything at once immediately just means the MC is not going to experience any hardship ever again. The entire univers bends over backwards just to please this guy. And all because he had to "suffer" that his amazing girlfriend wasn't able to deal with the stress of her situation and was a bit self centered.