Basic Trope: A hero, when being beaten, finds an inner strength and the will to win.
Straight: Bob is fighting Emperor Evulz. He's losing rather badly - until Evulz threatens Alice, Bob's wife. This causes Bob to find his resolve and kick Evulz's ass.
Exaggerated: Evulz is curbstomping Bob when he offhandedly threatens Alice. This causes Bob to start curbstomping him.
Downplayed: Bob's still standing, but he's losing steam, when a stray shot grazes Alice. Bob gets his focus back and resumes the fight.
The threat of losing Alice caused Bob to dig deep and find his inner strength.
Bob no longer cares about surviving the battle, and is willing to settle for a Taking You with Me.
Bob's abilities are psychoactive in nature; he was losing the battle because Evulz managed to crush his spirit with his Breaking Speech... But at moment he touched Bob's Berserk Button, he accidentally reactivated his special powers.
Bob is fighting Evulz pretty close, or even winning. When Evulz threatens Alice, this distracts Bob to the point where Evulz begins winning.
Bob tries to goad Evulz into attacking Alice, since she is the superior fighter of the two.
Subverted: Even with the added resolve, Evulz beats Bob anyway.
Double Subverted: Until he actually harms Alice, in which case Bob ignores any and all wounds.
Parodied: It looks as if Bob is dead. Evulz walks away, and slightly insults Alice's cooking. (And he was being "polite", because it REALLY sucks!) Suddenly, dead Bob is back up and curbstomping Evulz.
Zig Zagged: Bob is winning, but Evulz points to Alice who is in an inescapable death trap. Evulz begins winning while Bob tries to free Alice. Once she is free Bob again starts to win, but runs out of steam before Evulz can be defeated. Until Evulz leaves him for dead to attack Alice, allowing Bob enough time to get back on his feet and land the finishing blow.
Enforced: "So get this. The bad guy's going to win the fight for the first few minutes...then he's going to threaten Bob's most precious object, causing him to win. This way, both fanbases get what they want."