The top four villains for a suicide squad should be
1) Darth Vader - no villain is more iconic, and he is very badass because his use of the force is very awesome
2) Loki- another very iconic villain that is incredibly powerful. As long as Tom Hibbleston is Loki, he should be a lock.
3) The Witch King of Angmar- how awesome would it be to watch the Witch King flying on his dragon swooping in after Darth Vader used the force to take the down a whole load of enemies?
4) Juggernaut- juggernaut is the perfect compliment to the other threes abilities. All three are very intelligent. Loki can convince nearly anyone to help them out. Vader can take down nearly anyone in 1 on 1 combat. The which King can take down entire armies at a time. There is one glaring thing missing, however: size and brute force. While it may appear between the witch King and Vader, anyone can easily be taken care of. However, think about the Hulk. The only one who could would be juggernaut. Juggernaut possess something very valuable: size. He is incredibly large and very strong, and would be a great fourth addition