The only meaning of holding back your power is to not show it to your enemies too early and to have something in the back of your hand to surprise them, when the need arises. But hiding it until you get surprised or overpowered and to black out, just to be killed then, defeats the purpose of that tactic.
Also I agree on that thing about holding back, while people are dying to your left and right and not being fit to be a hero by doing so, that has been mentioned already several times.
And the sudden powerup for MC now is a total low quality asspull.