The manhwa stays true to the novel down to every single word as far as I can tell
OBJECTION ! in chapter 72 he said: "Mr Ki-Hoon, this dungeon is the Hunters guild's property. I cant just interfere. But this attack force is about to be wiped out. Let me ask you just one thing. Can i kill all the monsters present in this room ?"
In the novel there is only the last sentence, I was so excited when I was reading the novel at this part only to be a bit frustrated because this badass speaking was not here
As you said, the manhwa is almost carbon copy of the novel except for why the alliance of japan and korea for jeju island, in manhwa it's for the nation title of Goto and in the novel it's for "the control of korean portal by the japanese" (to make it simple)
I was obviously joking with the objection part, english is not my main language and I dont know if I convey well the joke