The Slowed-Down Time
The part where Jack uses his watch to slow down time, pick up Leena, and runs off, he first stops to stare at Whistler. He could easily, and I mean easily have killed Whistler right there, and mission complete. He could've picked her up, pulled out his gun, shot Whistler while holding Leena, then drove off.
My DVD collection:
http://mrdudeman.dvdaf.com/owned