When Linley or others get to the higher planes, cultivation takes hundreds/ thousands of years for improvements. Even early on in Invincile, that slow rate of improvement seems like it's gonna be the norm.
It was someone pretty "evil" and trying to kill the MC. Instead of him killing her off, he forces himself on her because of a certain situation. She lives and they both heavily benefit from what happened.
The girl that was raped, as weird as it may sound. Like I said above, the rape isn't as bad as people make it out to be, seriously, and nowhere close to as bad as other novels. Anyway, I quite like her and her interactions with Su Yun. They have the most complex relationship compared to the others and I just really like their interactions. Very refreshing haha.
The MC starts off as a reincarnated weakling in a world that's more than what initially meets the eye. He also doesn't start off really young as he's nearly 20, which is an older start for a CN. After realizing the worlds peril, he starts to get strong pretty quickly and has a pretty big transformation, physically. I likened him to Toguro from Yu Yu Hakusho, as I consider his body VERY similar to him. As a negative review mentioned, he becomes totally bald and gets increasingly muscular, but don't let that deter you (honestly, it made me more hype haha) as it doesn't last forever... Well, imagine all those other CNs where once you get strong enough, you can change your body. That's what happens, but that incredibly muscular form is more of his "true" form when it comes to combat... So, like Toguro haha.
His personality takes a bit of a hit as well. A genre tag is "horror", so you can expect the things he'll see and witness. He's not really evil, but the title "Way of the Devil" says a lot, personality wise AND physically. A lot of things end up being done mostly for his own benefit, as he can't afford to act otherwise.