Lucky good guys syndrome

A common story mechanism is that the bad guys are much better than the good guys. They have huge castles, or bazookas, or whatever the story calls for, and all the good guys have is that little heartwarming light called hope.

But somehow, through either 

A: the good guy finding a chink in the evil guy's armor, such as an off switch or a literal chink in his armor.

B: the good guy kills him using his environment, EG, in a factory, they fight on a conveyor belt, good guy knocks a vat of glue onto the bad guy, bad guy is stuck going down the conveyor belt to a certain doom.

C: "REINFORCEMENTS HAVE COME, WE'RE SAVED!" (which is always lame)

Of course, the whole reason the good guys are fighting the bad guys is because the bad guys are stronger. It gives the story a challenge. So it's pretty hard to avoid "Lucky good guys syndrome". There are ways, however, but if you can't think of one just make the environment kill (see B) extra cool.