Dragon

Moe(in dragon form) first appeared and died in Multiverse Travel Part 3. He was sent by the CCC to contain the Chaos, but he also had the same power of Thanos' Infinity Gauntlet, wiping out half of the population from a snap.

Victims
In Multiverse Travel Part 3, Dragon murdered many people in his snap. Off camera, half of the entire population was wiped out. However, on camera, he has quite a list of victims. These include, in order, Shadow, Brian/Drian, Bot, Tetris, Sans, Papyrus, Bird, Jared, and Hairbrush Bathmat.