That was my favorite part of a novel I was reading. MC was betrayed by his Fiance (childhood friend) who joined the Hero's party. While she was on that journey, MC trained and became the 11th S-Rank in the Guild. They established that the difference between S-Rank and A-Rank is "S-Ranks have the power to deform the surrounding terrain" and are basically one-man armies. It was even revealed that he was trying to make her journey go faster so he recruited two other S-Ranks who were bored and tried to go kill the Demon King themselves. Which they succeeded in, thousands of times, until the Demon King begged them to leave him alone since he couldn't be killed by anyone but the Hero and it traumatized him (and the Hero's party still struggled to kill him).
So when it came out that the "weak childhood friend" she'd been cheating on was this powerhouse of an Adventurer, the King literally punished both of them (and the Knight Commander who was sent to help keep them in line) and begged the MC to not blame the kingdom because they didn't know about the betrayal until they returned from the quest.
It was really refreshing seeing that the powerhouse MC was valued over the significantly weaker Hero. (tbf, the Hero was said to be top of A-Rank, but that's just how significant of a gap there is between S and A Ranks)
After the betrayal, he ran off and met up with some people that knew him and the ex-Fiance, trying to cheer him up they stopped by a town to go on a low-stakes quest, but MC (who's still not widely known in this area) has the standard "stopped by a tough adventurer for being with cute girls" scene and just flat out tosses the dude through the wall of the guild. The branch master storms down to find out what's going on and demands that he speak to her in her office and he goes "no. I'm going on a quest with my friends. He can explain what happened when he wakes up. We'll talk when I get back." She's dumbfounded and tries to assert her authority as a branch master and says she'll stop him by force if she has to. He literally goes "You're not strong enough. Even if you got all the adventurer's in this town to work together, I'd be able to wipe this town off the map in under 5-minutes. Now, I'm going on a quest with my friends. We'll speak when I get back." While he's gone she gets the report that he's the newest S-Rank and gets reprimanded for trying to assert authority before getting the full story. (she was literally just promoted to branch master and didn't want to seem like a pushover, which backfired because she couldn't read the room.)
It's seriously refreshing to see an OP MC act in a way that shows they know they're OP. Apparently, he's on the weaker end of S-Rank too. But we haven't seen another S-Rank yet in the story
