Found on reddit.
Seems Etrigan, Blue Bird, Krypto, Constatine, Detective Chimp and even Penguin were supposed to be DLC characters for Injustice 2, but eventually got scrapped.
Link: https://www.reddit.com/r/gaming/comments/9nnbrl/concept_art_for_scrapped_injustice_2_characters/
Hopefully some of these guys can make it into IJ3.
Seems Etrigan, Blue Bird, Krypto, Constatine, Detective Chimp and even Penguin were supposed to be DLC characters for Injustice 2, but eventually got scrapped.
Link: https://www.reddit.com/r/gaming/comments/9nnbrl/concept_art_for_scrapped_injustice_2_characters/
Hopefully some of these guys can make it into IJ3.