Your best choices are Iron Hammer, Shuri, or Skurge. Iron Hammer is strong and easy to use. Shuri at T2 gives your team a bonus versus villains just by being on the team...and she's not bad as a character herself. Skurge is a villain, which will be very useful when you start doing game modes with requirements like Alliance Battle Extreme and Shadowlands. Skurge does need to be T2, he sucks at T1.