5. Belasco
The Marvel universe has its fair share of demonic characters, though among the most interesting and amenable to Bryan Singer's vision of the X-Men franchise is Belasco, a former sorcerer who made a deal that imbued him with a Devil-like appearance and abilities; in fact, he might even be
the Devil we know of from the Bible. Though not inherent linked to Days of Future Past in the comics, it would be easy to tie the character into the Sentinels, using them to his own will. The bigger concern would probably be in streamlining the character's demonic aspects to suit Singer's more pared down, pragmatic take on the material. Practically speaking, Dinklage would, like with Ahab, not be limited by a physical human form; performance capture would make this totally work, and we have no doubt Dinklage could lend an appropriately menacing voice to one of the X-Men's most twisted adversaries.