Which character do you think has directly killed the most characters with Legendary Creature cards? (Inspired by the cause of death segment in your ongoing dead legends Twitter thread)Most confirmed Legend kills is a tough number to hit, because do you count indirect kills? I also may have mislabeled a death or two to not make it easy to attribute it to a character. And what about assists? Now, my numbers aren't perfect because I don't have a good attribution system, but here are my thoughts.
Tetsuo Umezawa has the most
direct kills. As in, he's personally killed five other Legends: Xira Arien, Boris Devilboon, Ramses Overdark, and Orca, as well as Nicol Bolas, even if Bolas got better.
Liliana Vess has personally killed Josu Vess, Kothophed, Belzenlok, and Griselbrand, and killed Razaketh in a team effort with the Gatewatch. She's up there too. There's probably more I missed.
Kaya is no slouch either, with four confirmed direct kills in Brago, Grandfather Karlov, the Obzedat (if we only count it as one), and Heliod.
Kamahl, Crovax, Halfdane, Liliana, the Scorpion God each have three solo kills
Nicol Bolas hasn't killed Legends directly very often. He killed Bontu directly, and through the Scorpion God, three of the other gods. He'd also twisted the original three Insect gods, although we never see those forms. And through minions he killed Jazal Goldmane and others, it'd be hard to get an exact figure. He's definitely responsible for the largest number of Legendary card deaths, even if he didn't directly kill them all.
Yawgmoth in his deathcloud form is confirmed to have killed Eladamri, Lin Sivvi, and Galina. He also indirectly killed Glacian and Rebbec with his bombs, but the bombing was at his order so I'm counting it. That's at least five, probably more (ESPECIALLY if you include Phyrexia and if we include Bolas minions, we kind of need to count it, right?).