how do i gain momentum i want to do a punch and rip apart by punching but i need more momentum

You need to use every joint, even relaxing or extending the wrists or ankles can help.

k

relaxing ur knee helps with a roundhouse kick
ur more likely to split the person

Post a replay of a punch attempt so we can actually see how good you are and where your mistakes are.

here ya go

Important: Do not bend your knees. A lot of the power and rotation comes from the hips and glutes, bending your knees loses you that power. Take a look at my replay and press 'e' right before the punch. You can see I am using nearly every joint. Ask me which one does what if you are confused, or study them yourself to see what you have to move to generate power.

If you use that contracted knee opener you have to make sure to get them in a suitable situation (use hips and glutes) and extend them while punching.