I haven't been catching up with the recent chapters but excluding that
The novels like wayy darker than the manhwa, the manhwa always portrays them as goofy and like kinda nonsensical almost. Hayan is likeable in novel as compared to manhwa imo, in the novel, she's portrayed as a mentally unwell girl who's failed by everyone and got into bad hands that is ky.
There are some parts in an arc that's omitted. The ones i remember is, hayan keeping a watching eye on ky, wayyy back when her and deokgu were training i believe with hy, and during that time, ky practices and reaches a new level/i think earns a title or something. Also the saint/sun heeyoung, she was recruited differently in the novel, which is a bit dark but it still made sense and i think fit the theme.
There's also 2 implied SA which idk if it's a good or bad thing they omitted. Also seems the recent arc just removed the hyejin and kys friendship, which was an amazing small arc, it also contained jihye being very nice towards hyejin too and showing hy in a new light.
I might be wrong about this, but i think the alice/oscar part wasn't as same as the novel since she had a very good emotional rollercoaster of emotions and hard decision making in the novel. I think also the flashback to the first timeline might've been more impactful in the novel, i remember absolutely liking ky cause it genuinely seemed like he was reasonable with his anger.
Again, since the manhwa portrays our mc as a goofy character, many people come to hate him. In the novel, our mc is fully aware about his selfish behaviour but that comes from his inner insecurity and to make up for that, there are many instances where kiyoung genuinely works very hard to the point it says, he neglects his own health.
I think there's much more, but i haven't properly read the manhwa for a while and so things are just blurry
Ive been reading tcf and rim, they are absolutely my favorites. I see how the manwha adaptation if tcf is very good(of course, there are some complains) and rim is so ahh. Ky is a funny guy,made me laugh a lot on the novel,but he is not this fool like in manwha. The """ky and hsg divorce arc"""" is such a sweet memory to ne reading,and niw is just bad

I'm so disappointed rn,Rim is not that famous compared with others Koreans stories,but it really have a place in my heart. I wish they could attract more reader with the manwha version,but is just so bad. Without foot or head,they just going for another direction I guess. Fist the trial against the japanese dude,then we have Han Sora arc,now this. They are all arcs that I love and I just feel so bored with how they interpreted in the manwha