The coin has exactly 2 sides. Tossing a coin every time, you have exactly 2 options that can fall out: obverse or reverse. Accordingly, every time you throw a coin, you get 2 equally probable options.
100%: 2 = 50% for each option, in any of the selected shots.
Two faced a character in the Batman series uses a toss coin to make a decision to kill someone, so even if he wants too kill Joker he has no choice but to abide by what the result of the tossed coin, so for me it's 50-50% that you will win unless you are good at tossing coin and you can manipulate the results.