A Combat Trope in which one of the combatants reveals that (s)he's been holding back, but now decides it's time to take it up a notch. The situation varies from example to example. A common example is for a character to fight with his non-dominant hand, as in the trope-naming example, only to switch back to his dominant hand to gain an edge. Similar to this is pretending that he has a serious handicap, then deciding to stop the charade -- in other words, a seeming in-universe equivalent of an Unexplained Recovery. It can also go so far as a character revealing that he has always had a superpower which they now decide to exploit, or a Dangerous Forbidden Technique which they now have no option but to utilize.