The 11th (or so) chapter called "Friendly Combat" and consists of Carla and Tyler in a gym getting ready to work out. You get this achievement for winning the sparring match at the end of the workout.
The sparring match is simply a series of QTE's. If you do one successfully, Carla gets a point. If you fail, Tyler gets a point. The achievement unlocks if you get Carla to 10 points before Tyler.