I have this idea of a story about a man whose an F-ranked adventurer who wants to party but no one wants to be with him. After rumours spread, they told about how he is the most useless person apart from being a pack mule which is why he is always an F-ranked.
For shts and giggles, a group partied up with him, only to be used as a meatshield as they decided to throw him into a boss room while they gather the treasures and GTFO. The plan worked and they began to laugh, thinking that it was so easy to get money by sacrificing someone.
Next day, they were scared shtless after the guy came back, wanting to party with them again. Like, he was literally sacrificed to get easy money and he just came out of nowhere, not even injured at the slightest.
There, evil people began to try and use him when he only wants to get promoted to D-rank and try to ask his crush out.
His power? Power Overwhelming
The more dangerous the MC's situation is, the more power he gains. The downside is that he can't be strong against those weaker than him.
Like, a single scrawny goblin can kill him instantly but an evil god with OP powers would be One-shot by the MC without a sweat.
The cheat slayer. Built to kill OP characters not built to survive an easy situation.
It is the main reason why he can never go above F-rank since you need to solo a quest to get promoted and even the easiest F-rank promotion would get him killed.