None of this has anything to do with moves or fighting ability, for me Mortal Kombat has always been about the lore, not the move-set. Why, because if a character sucks, just give their moves to someone similar enough and problem solved. But you can't change much about a terrible character if they're just awfully designed and written. There's no saving Jarek or Khameleon no matter how many moves you give them from other fighters.
So I say...
Kollector, Geras, Cetrion, Erron Black and Jacqui.
Kollector is just a greedy skinny Shokan. Utterly utterly rubbish and devoid of decent ideas "Hey team, new character idea, hear me out: Shokans had 4 arms... this guy has 6 arms! But you can only really see 4 of them... what do you think?" Just give us a well designed Sheeva instead.
Geras, large stoic man with lines on his face. Apparently a time lord; reality just a bland hoss.
Cetrion, I like the idea of Shinnok's sister being a vessel of merciless single-minded conviction in the name of "life". It's an interesting moral duality, she destroys in the name of moral righteousness. Reality, just a lady in toga who controls the same elements that all the ninjas did separately... and can't walk properly.
Erron Black. Cheesy Mad Max cowboy. Awful, just awful. Get rid of him. Give his move-set to literally anyone else with a gun. Ugh, he just looks pathetic - granted he looks better in Mk11 and MKX where he seemed even more of a tacky looking try-hard, but I still thoroughly hate him.
Jacqui, just blah. At least Cassie has sass and some character to her, she may be rather irritating millennial social media valley girl douche, but hey, it's a new persona for MK. Jacqui however is just so bland and pointless, a character who does nothing, has nothing, says nothing, she just "is". Army girl with zero personality.
That said, I still prefer all of the above to the worst characters in the 3D era. I don't think we're at Taven, Darius, Hsu Hao, Kobra, Jarek, Kai, Reiko and Li Mei levels of barrel-scraping anymore. Just the above don't feel like they're really every going to go anywhere... oh and I just hate cowboy characters regardless.