Online trope compiler TvTropes has decided to call this one Dog Pile of Doom:
A large number of mooks jump on the hero, pinning him down.
Usually it's a climactic battle scene. The hero is facing down dozens, no, hundreds, no, THOUSANDS of Mooks. At first, the hero's doing well. He's smiting them one after another. But then he begins to get tired, and first one, then another, then another and another and another leap onto him, dragging the poor guy to the ground.
It seems you're after the first scenario mentioned there:
There are several ways that this scene can turn out:
Type A: The hero activates a super mode, has an epiphany, or otherwise becomes more Bad Ass. He explodes out of the pile, minions scattering to the four winds, and rises as an epic figure.