This is a guaranteed unlock when you play as the Hulk in the opening segment of the game.
The beginning mission where you play as every Avenger in succession will eventually land you to traversing a broken bridge as the Incredible Hulk. You will be given an opportunity to learn the controls and features of gameplay. The Thunderclap move is Hulk's R1 + L1 ability. You will be prompted to do this move and it will defeat every enemy ahead, which is scripted and has more than 10 enemies.