2) The Riddler
Like Mr. Freeze, The Riddler has shown up on film before and is also featured on the small screen in Gotham, but we still have yet to see a solid portrayal of the intriguing villain in cinema. For the character to work, they have to make him as twisted and psychotic as possible, and have him really dig into the psyche of the audience and Batman alike.
[zergpaid]Of course, this mostly depends on the actor playing him, but some of it most definitely comes from the writing. If they can nail that aspect of him and show us the psychological torment that he’s capable of inflicting on Batman, then there’s no reason that he couldn’t go onto become one of the most threatening villains in DC’s Cinematic Universe.