Blue slimes are the weakest. But, they have the ability to eat nuclear warheads. And that changes some things.
Also, I'm enjoying the story so far, even with the clichés, but then, I've always enjoyed the "I reject the call of destiny, stop texting me, I want to live peacefully" style of protagonist. The MC has a good motivation for making interesting decisions, and he's not a massive pussy or some sort of cringelord.