Successfully complete the indicated task to unlock the corresponding car:

Assassin Compact: Get 15 Takedowns.
Compact Collector: Win the Gold medal at the Silver Lake Eliminator (type varies in each game).
Compact Cop: Win the bronze medal or higher at the Silver Lake or Airport T1 and T2 Pursuit.
Dominator Compact: Get 10,000 Burnout Points.
Gangster Legend: Win the gold medal at the Palma Bay Legend Face-Off.
Legend Compact: Win the gold medal at the Interstate Loop Legend Face-Off.
Tuned Compact: Win five gold medals.