>>712600162
Took you this long? He's the guy who threatens your life on a pacifist run but sits back and does nothing as long as you're arbitrarily neutral enough, even when you kill so many bosses the underground is rendered completely leaderless
He's a self-righteous asshole who only bothers to do something when he's been given no choice but to. And no, a promise to Toriel isn't a good reason to let the player murder his brother in cold blood.
In deltarune, he has no reason to want to be nice to the player, so all you see is his dickish attitude