If that happened, I'd be at your mercy.
5 seconds sound clip from the Five Fingers of Death movie soundboard.
You can hear this line at 00:04:54 in the DVD version of the movie.
Quote context
[...]
- Well with a teacher like that, you must have improved a lot.
- By next year, you'll be good enough to be in the tournament.
- If I am able to, I'd like to have a go.
- Just think what a match it would be if you two had to compete. That would be something.
- If that happened, I'd be at your mercy.
- Not at all. You could teach me a lot.
- You two haven't fought each other for ages. Why don't you have a little match?
- All right. Later. I'd be interested to see how you're getting on.
(KUNG-FU FIGHTING WITH BARE HANDS)
[...]