Sans’ battle in the genocide/no mercy route is by far one of the coolest fights in Undertale (also kinda depressing lmao).
I mean, right off the bat, he doesn’t pull any punches, and it’s surprising considering how much of a laidback kind of guy he is. For all his corny jokes, and easy going, friendly attitude, he can be pretty damn intimidating, and a badass to boot. his battle is especially impressive considering he's got some of the lowest stats of any boss in the game. despite that, his fight is considered the most difficult, as well as the longest, because it lasts at least 14 minutes.
So yea, even with a big ‘ol smile plastered on his face, the guy’s got no chill whatsoever, and that’s one of the reasons he’s easily my favourite character.
Undertale © Toby Fox