Here is the full list of all 12 Tennis in the Face achievements.
In a level with at least three enemies, knock everyone out with the first serve.
Knock out 5 enemies before the fourth bounce.
Earn at least one extra ball from every level in the first district.
Score 25,000 points with a single serve.
Get five headshots with a single serve.
Serve a ball that bounces 100 times.
Knock out six opponents with a single Explodz explosion.
Destroy 10 pieces of glass during one level.
Earn 1,000,000 points in the main menu.
Destroy three vending machines with a ball and a single serve.
Defeat the 10tons crew.
Collect three briefcases with a single serve.