User blog comment:DewK357/Villains in Arkham Knight/@comment-14214626-20140315200511

I think that Rocksteady should make previous playable characters to make a comeback, the characters listed with "Free roam" as the name suggests, are characters that you don't need to have an especific objective to use them, while the ones listed with "Challenge maps" do.

Batman Arkham Knight Playable Characters

Batman (Free roam)

Robin (Free roam)

Harley Quinn (Free roam, Pre-Order DLC only)

Catwoman (Challenge maps, DLC)

Nightwing (Challenge maps, DLC)

Arkham Knight (Challenge maps, DLC)

As you can see, i've maked a list about characters you can fight, with the character(s) who can fight them listed next to them.

Batman Arkham Knight Bosses

Arkham Knight (Batman, Harley Quinn)

Scarecrow (Batman, Robin)

Harley Quinn (Batman, Robin, Nightwing, Arkham Knight)

Bane (Batman, Catwoman, Arkham Knight)

Killer Croc (Batman, Harley Quinn, Arkham Knight)

Riddler (Batman, Catwoman, Arkham Knight)

Two-Face (Batman, Robin, Catwoman, Arkham Knight)

Penguin (Batman, Robin, Nightwing, Arkham Knight)

Copperhead (Harley Quinn, Arkham Knight)

Clayface (Nightwing)

Poison Ivy (Batman, Robin, Catwoman, Arkham Knight)

Firefly (Batman)

Ra's Al Ghul (Batman, Robin, Nightwing)

Batman (Harley Quinn)

Robin (Harley Quinn)

Nightwing (Harley Quinn)

As you can see, Harley and the Arkham Knight fight a lot of villians, that is because it is when the Knight is forcing them to support him or else he will kill them, while Harley is "having a little chit chat" with them about joining the a certain squad ;), wich might lead to the events of the next Rocksteady DC game.

Still i think there will be some Cameo characters that will either help or attack you, they would be kinda of like the Sub Bosses of the game, like Hush ( don't see him like the AK, sorry : or copperhead for Batman before he faces Killer Croc.