Actually this version of the Legion of Doom is made to be like the exact opposite of the JLU, which means there are like 30 members in the group.
This is a list of villains one person saw in the episode preview at the San Diego Comic Con. Remember this is not a full list and some characters might be mistaken for others
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...wait a second...
How did
break out of his craziness?
..and that group would be SO much better with Joker. ...almost everything's better with Joker. Except his sidekick Harley. She's fun by herself.