13 Marvel Villains Still Alive In The MCU (Who Could Return)
12. Justin Hammer
All of Tony Stark's villains have been mirrors of him in some way: Obadiah Stane was the natural progression of what Tony would become if he had remained a weapons-selling businessman; Aldrich Killian is a genius, playboy inventor; Ultron is Stark as Dr Frankenstein to a bigger degree and Thanos is his extremism personified. Justin Hammer was the most obvious "clone" of Stark, though, since he was his business rival and effectively wanted to steal his position and his marketshare.
Where Is He?
After teaming up with Whiplash and finding himself arrested, Hammer was thrown into Seagate Prison, but kept secret from the general populace. After vowing revenge on Tony Stark, he then reappeared in the All Hail The King one-shot expressing his jealousy at Trevor Slattery's fame within the prison.
Not as high as he probably believes, but Hammer's wealth makes him a problem if he ever gets out. Were he able to work with someone like Ivan Vanko again - though less flawed - he could be a danger to the Avengers.