Mitch Wilkinson
He was a ridiculous, poorly written character and one of the film's chief flaws.
For the entire movie, he's portrayed as nothing short of nefarious. He knowingly and falsely accuses Gates' great-grandfather of being the mastermind behind the Lincoln assassination. He coerces the museum director into going along and publicizing the diary page implicating Thomas Gates. He breaks into Patrick Gates' home, has him assaulted, and surreptitiously clones his cell phone. He starts a dangerous, high-speed car chase through the crowded streets of London. He threatens Gates' mother with a gun and threatens to murder her ex-husband. He holds everyone at gunpoint at Mount Rushmore, then, once they reach Cibola, he attacks Riley and Gates and holds Abigail at knifepoint.
Yet, in spite of all of this sociopathic behavior, we're to believe he suddenly experiences a pang of altruism and decides to sacrifice himself for the Gates clan -- despite the fact that just moments before he punched Gates in the face and stuck a knife to Abigail's throat in order to ensure his own exit and survival. Not only was his "sacrifice" unexplainably out-of-character, but did the writers really expect the audience to ignore his villainy from the first two hours and feel sympathy over his death?
Ian Howe was a far superior character and worthier adversary. Mitch was a cartoon.