As a rule, much of fiction ends with the villain being defeated by the hero. This should be dramatic, but if the true villain isn't that physically powerful, then this is going to be a rather short fight. Either way, the hero will eventually get a dramatic burst and fight on despite his weakened state, and will usually defeat their foe by the slightest of margins. Only once they've won will they be allowed the luxury of collapsing. For a truly Bittersweet Ending, they might never get up again. Examples: