I m glad beastboy won't be in this game. He is easily the cringiest character some people have been asking for. I can imagine him sitting somewhere in dirty sewer picking his nose because he got rejected.
Kano another noteworthy mention, but Cage v. Kano have awesome dialogues.
Liu Kang/Mileena/Kitana have hilarious ones when paired together, one where Mileena gets excited to meet "her sister's boyfriend (Liu Kang)"
But I think Harley will have some dope shade to share in IJ2