The Penguin.
>The Joker
Crazy as fuck. Will probably not care if you die, or kill you himself.
>Poison Ivy
Doesn't have a crew. Also hates most/if not all Humans.
>Cat Woman
Doesn't have a crew and won't make one. She goes solo. You'd slow her down.
>Harley Quinn
Doesn't have a crew, she's usually in someone elses. She'd probably be pretty fun though and much less likely to kill you than The Joker. Evidently cares about other people. Probably not a smart boss though.
>Mad Hatter
A Genius, highly intelligent and probably willing to let you be relatively normal. Might just mind-control you if you ever talk back to him though.
>Man-Bat
He's the Man-Bat. No crew. Will probably kill and eat you.
>The Scarecrow
Not very likely to kill you. Treats his Men well as far as I know. Biggest risk is getting caught in his Fear Gas or something.
>Two-Face
Usually a good boss, you can be relatively normal and casual If you're fine with his potentially ignoring choice opportunities to capitalize on something because of a coin-flip, probably a good choice for a boss.
>Mr Freeze
Cold and indifferent, if you make a mistake he WILL leave you to your fate. If you're fine with being condemned to your own fate if you ever fuck up, then might be a good boss. Things will get really fucking cold around him, so dress warm at all times.
>Clay-Face
Doesn't have a crew, but if willing to make one and you've got ideas on how he can capitalize on his shape-changing abilities, you can probably become a very successful group.
>The Riddler
Lots of good plans, but his own sense of honor and pursuit of a challenge will always lead him to give his adversary a fighting chance. You will probably be allowed to just be yourself as part of his crew/around him. If you're fine with there usually being a not 0% chance of failure, then go for it.
>Killer Croc
Doesn't have a crew. If he's willing to form one with you as the idea guy/advisor then you might be able to get shit done, though.