It's a tough choice to pick between villains and you have to consider what they can bring to the table. You also have to figure what they have done in the past and make sure they don't end up betraying you in the end. I think you have find that common enemy or idea to take down to have a great allies.
My First Pick is... Bane (The Dark Knight Rises)
Why? His Strength is so powerful and I believe him to be a worthy of my Suicide Squad. His brutality could help bring some people down and corrupt them into joining our side or dying. In The Dark Knight Rises Movie, if you can remember he broke Batman Down literally and threw him in a hole where he had to super train himself back to get out of the hole.
"I'm Gotham's reckoning, here to end the borrowed time you've all been living on."
―Bane to John Daggett before killing him
My Second Pick is Gannondorf!
This guy is Badass! Ganondorf is main Villain is most Legend of Zelda Games. He controls monsters and is powerful with the dark magic.
"The Triforce parts are resonating...they are combining into one again. Those last two pieces that I couldn't get on that day, seven years ago...I had no idea that they would be hiding within you two! And now all the pieces have gathered here! These toys are too much for you! I command you to return them to me!"
Here's a funny little video from a Youtuber called The Hyperbolic Bubble:
(Warning: strong language)
you may or may not think it's funny.
My Third Pick is Crowley
I choose him because he an honorable and reasonable man. In the recent supernatural, you'll see his true colors.
Don't worry about -- what, like Lucifer didn't worry? Or Michael? Or Lilith or Alastair or Azazel didn't worry?! Am I the only game piece on the board who doesn't underestimate those denim-wrapped nightmares?!
– Crowley, 6.20 The Man Who Would Be King
My Final Pick is Hannibal Lecter
Team needs someone who has already won the game before the opposition even knows their playing. He is going to be the brains of the operation.
"Who's hungry?" -Hannibal Lecter to a Group of Patrons.
Who can deny that innocent looking face, hehe.
"He looks normal. Nobody can tell what he is." (Will Graham)