I feel like Boundless Hero fits your request like a glove. The book is exactly what the title suggests. No villain, no antihero, just a good guy doing what he has to do.
I read a litRPG cultivation story where the more powerful the MC gets, the more he loses his humanity. His whole way of thinking changes. He doesn't like it, either, but he needs the power for plot reasons. It was pretty good, called Boundless Hero
My recommendation has no harem, a tiny bit of background romance, and a humorous concept played straight (the main character is addicted to cultivation webnovels, which actually factors into the plot). I quite liked it. It's called Boundless Hero
There's a scifi xianxia novel called Boundless Hero. The MC is a webnovel addict lol. Not very long, but fun
Boundless Hero is a fast-paced scifi cultivation novel. Very shonen. Pretty much nonstop battles and training.
