As fans will remember all too well from Season 2's "Mortynight Run," Krombopulos Michael met up with Rick to secure a secret weapon for a hit job. Morty didn't like being part of such a nefarious mission, so in an attempt to try to do the right thing, he kills Krombopulos Michael and releases his target into the universe.
Krombopulos Michael didn't get a ton of screentime, but he made the most of it with his now-iconic catchphrase, "Oh boy, here I go killing again." Undoubtedly, there could've been plenty more adventures with the hitman, but it doesn't seem like we'll get any more of those now that he's dead, and fans have voiced their displeasure at that development online. In a Reddit thread, u/Homelss_Emperor writes, "The worst thing this show has ever done was kill off [Krombopulos Michael]."
Others tried to look at the bright side. After all, "Rick and Morty" regularly plays around with the idea of the multiverse, so it's possible another version of the character could enter the main continuity. Redditor u/Dafracturedbutwhole explains, "He only died in 1 universe. There are a lot more [Michaels] out there from Krombopulous to Jan-Vincent." While it's unlikely the show will journey back to the Krombopulos Michael well, at least we can always revisit "Mortynight Run" whenever we need to be reminded of how much the character enjoys killing.