I pretty much share your list, they're all good choices. Here's my top:

Batman:

Mr. Freeze
Poison Ivy
Scarecrow
Killer Croc

Superman

Cyborg Superman
Bizarro
Parasite
Brainiac

Hi guys it's been a while.

Red Hood and silver banshee would make interesting bats/supes villains!

Welcome back!

Batman villians:
Red Hood
Mr Freeze
Poison Ivy
Two Face
Ra's al Ghul

Superman:
Darkseid
Bizarro
Brainiac
Lobo...yeah, I know he was in the first game. Don't care, Lobo's awesome.

Some good suggestions so far.

Batman

The Penguin
Mr Zsasz
The Riddler
Talia Al Ghul
Man-Bat
Clayface
The Mad Hatter


Superman

Granny Goodness
Mister Mxyzptlk

Forgot about Clayface. He would be amazing!

Penguin! Trick Umbrellas please!

This! Different umbrella builds please! Some shoot bullets, some shoot lasers, but they all deflect!

I have little to no knowledge of Superman's universe, but from Batman I really really want to see Penguin, The Riddler, Poison Ivy, and Mr. Freeze or Clayface.

Superman: Parasite

Batman: Poison Ivy

Wonder Woman: Cheetah

Being more exclusively a Batman fan, I would say that although I definitely want love for his villains, I really want to see more unique DC characters too by saving them some spots, such as Dr. Fate. Honestly, he would be a badass.

SO, if I could choose, besides the inevitable Batman, Joker, and Harley (and maybe Catwoman and Nightwing/Robin but I think those two could actually be left out), then first of all, I would replace Bane. I think he made it in the first game because of his recent appearance in TDKR so he was riding on that resurgence of popularity, but now it's time to replace him.

I would be happy with either:

- Poison Ivy - very obvious choice to expand the female roster AND the ability to control plants is extremely unique)

- Killer Croc - replacing the muscle character of Bane, except he could have many moves that involve biting and impaling with long claw-like fingernails)

- Mr. Freeze - I can imagine him being a mix between a heavy-hitting character like Grundy or Bane with his mecha suit and yet having abilities akin to Killer Frost. However, to expand the rogues gallery of other characters I would have to choose Captain Cold over him to allow for another Batman villain to take his place.

- Clayface - This one could be the most creative! From a gameplay point of view, I can imagine him turning his hands into various weapons or launching attacks out from within himself. I've always thought of Clayface as being an extremely powerful character, and I even think he could replace Doomsday as a sub-boss type character.

If really think that Riddler, Two-Face, and Penguin, as popular as villains as they are, would be very terrible choices with little to offer for the game's diversity. Mainly because they're just too... human-y? Unskilled in fighting in any way besides normal guns? And not the FUN guns like Deathstroke

I thought about Scarecrow too because the fear gas is an interesting concept but I can't really imagine how, besides limited use of the gas, he would play into a fighting style and could really be a fun-to-play character. His power works more on a mental level than a physical one for a fighting game.

Why remove Bane? He's got a great design and gameplay.

And about Riddler, Two-Face, the Penguin and the Scarecrow, people were also skeptical about The Joker and Lex Luthor being playable in fighting games before their inclusion in the MK/DC crossover.

Little to offer for the game's diversity? Are you kidding? They would diversify the game.

I believe that the simple inclusion of a yellow ring would make the mental powers of the Scarecrow in physical.

^ Hey, now there's an idea! I don't know if they would replace Sinestro to do that, because I think two Yellow Lantern characters might be redundant when another character could take that place, but Scarecrow with a ring? Sounds AMAZING! I know he did get a ring one time too temporarily in the comics!


Well what I mean with Bane is that the roster is only going to be so limited, and so the more returning characters there are, the less likely we'll get to see new faces. Bane was one of my favorites in Injustice 1, but if to add more NEW Batman characters to the game without overtaking too many roster slots with Batman-related characters, I would trade Bane before Joker or Harley. Especially for Croc because I would really like to see an Arkham Asylum-style version of him that would probably be fairly close to Bane's fighting style in terms of being a brute and could also use biting/clawing to shake things up. But assuming it's a limitless roster? No problems with Bane.

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Well having read comics and watched the old cartoons for years as a kid, Lex wasn't much of a surprise as a fighter because he's been heavily depicted as being in a battle suit for a few decades now. And Joker IS one to worry about going toe-to-toe with Superman, and I understand the Kryptonian drug explanation they have, but I think Joker fit more because he has had tons of gimmicks, such as laughing gas, joy buzzers, a boxing glove, cyanide pie, acid, and various zany rockets and missiles to name a few.

Penguin and Two-Face and Riddler are on the same strength level, but I just think it's harder to readily imagine the kind of specials they would have. Penguin would be easiest with the trick umbrellas, I will admit! But I also don't know if he's really THAT popular to take a spot over someone with more obvious specials like Poison Ivy. Two-Face? I don't think he uses anything besides guns, and I don't know of any other flashy gimmicks NRS would use him for that are coin-related. Riddler is more of a mental-level villain, and I can soooort of see how some trick-based, question mark-based weapons could be used, like a question mark cane, but it's also hard IMO. Mind you, Joker is sometimes depicted as being unnaturally strong despite his lanky appearance or able to withstand pain thanks to how over-the-top insane he is, and these villains have been in less physical circumstances besides using their goons. Not saying it's impossible though.

I know he's not a villain, but I wish we could get to see Swamp Thing.