Thunderbolt - Shia Labeouf
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Not because he's that great of an actor, but because he's hilarious and has a surprising range when he's performing. That, he has a ton of experience dealing with CGI, which would be vital for any CAH film.

Boom - Kate Beckinsale
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She's a great actor who knows how to do action very well. Her role in the Underworld movies would serve her well when it comes to playing a speedster.

Polemos - Adewale Akinnuoye-Agbaje
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He was born for the role. I had Polemos pegged for someone else, but after discovering Adewale? I'd never go back.