Good guy vs. Bad guy. The villian is much stronger and more skilled than the hero, but somehow the hero wins anyway.
Usually there is a scene near the end of the movie, where these two fight and the villian is superior throughout the fight, but through some good luck and coincidents the hero suddenly defeats the villian. Why not let the hero kill the bad guy in one blow for once?
Batman vs. Random Villian (Although Batman is quite easy to beat in a one-on-one fight he always wins.)
Terminator T-101 vs. T-1000