The ruthless route ending is absolutely amazing, it's very easily my favorite "segment" of the game so far and it's extremely well written. It pays off on a lot of mysteries set up before and fit a ton of hints on the true nature of the way the hotel works and everything about Argos, and previous scenes/plot points (like Argos's reaction when you trick him twice, the oddities about the many Argoi that came before) fit perfectly with the execution.
The things that jump out to me a loot though, and that i genuinely think will be major points later in the story were the narrator reveal - which was incredible, and extra props to the writer - and the much deeper detailing of how "magic and gods" wok. This latter, specifically, I suspect will be a key part in loophole-ing Asterion out of his sentence, even beyond what is already done in the good route.
All in all, it's a amazing payoff for going through the route, and do get me much more hyped for seeing how the other paths will wrap up.