The Boss (Metal Gear Solid 3: Snake Eater)
Naked Snake had nothing but the deepest of respect and admiration for the Boss, a woman who had been a mentor to him. So when she ended up selling out to the commies, Snakey Poo went a bit mental.
Then again, her betrayal was ultimately revealed to be a plot by the U.S. government, and when it came time to die for her country, The Boss did so gracefully and with a sense of style. Of course, Snake didn’t figure it out until after he had played an essential part in her execution, and this fact would haunt him for the rest of his life.