Mas Fuerte 2K is the set of two machines in the Arcade's back corner with the hammer and Strong Man tower. The way the game works is spamming as many buttons as you can on your keyboard and mouse simultaneously while still remaining within the shifting circle as it moves away from your cursor.
You will get two attempts per play, and the color of the screen will change as you spam more keys and amp up your "power." 90% or more is in the final, red tier. Keep practicing until you can get there.
Make sure you're spamming across your keyboard with your left hand and all five fingers, and are clicking both buttons on your mouse with your other hand. Moving your hand further up on the mouse will help, as you will be controlling your cursor with the weight of your arm and letting the rest of your right-hand fingers focus on spamming keys rather than guiding the mouse with your wrist.