When someone rushes in with overwhelming force, you use on of the corner techniques.
The way you described it above, it sounded like the person ran at you or something. (moving step Push Hands?)
If something like that’s the case, use Pulldown and Split.
Let’s say you are in a left foot forward stance, ready for a fight, as many people do not stand strong hand forward.
When he rushes in, you take a step back with the left foot and use P’eng to deflect his punch. Then you take a step back with the right foot, so that you are again in a left foot forward stance, grab his wrist with your right palm and his elbow with your left, and pull straight down to the ground. You do not pull towards you or past you to the side, you pull straight down. Your left hand will pressure his elbow downwards, and your right will actually pull upward slightly, so that he will turn and plummet face first into the ground.
If you cannot for some reason pull straight down as in the above, then you would have to resort to pulling him toward you. If you have to do this, you should twist his wrist with your right hand and, keeping his elbow locked with the left, shove his arm back up into this body. You will actually be spiralling his arm back into him. This is Split.
The key to both of these is to face the corner slightly and send the force into the corner, not actually right at him. For Pulldown, this makes your left palm, the one at his elbow, begin to hyperextend it, so that you could easily break his arm. For Split, you are doing the same, but the energy travels in a spiral, not a line. I’m not going to tell you the theory behind Split, because it sounds like bull, but if you crank the wrist twist, push his arm straight into him with your right palm, and maintain corner oriented pressure on his elbow, you may very well dislocate his shoulder. (This is the theory in layman’s terms, aren’t you glad I didn’t just say to divide the incoming force at the elbow and send it back to him in two different directions?
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Or, you could use P’eng to deflect the incoming strike, an oppressed block with the other hand (going beneath your P’eng), swing step your forward foot behind his lead leg, and give him the old clothesline.
Or you could do Rollback, pulling him towards you, letting go just after the pull and giving him Chee in the throat.
For these last two, he’ll end up sprawled on his back wondering what the hell happened. All he’ll remember probably is a rough landing.
“To enter is to be born, to retreat is to die.”
-An Old Taijiquan Saying