Here is the full list of all 30 Bullet Time Battle achievements.
Kill first enemy
Kill 5 enemies
Kill 10 enemies
Kill 30 enemies
Kill 50 enemies
Kill 100 enemies
Kill 1000 enemies
Plant first Bomb
Defuse first Bomb
Start Bullet Time
Stop Bullet Time
Capture a Blue Flag
Capture a Red Flag
Collect a weapon of Box
End a round
Kill 5 enemies at once
Kill 15 enemies at once
Kill 25 enemies at once
Capture 3 Blue Flags
Capture 3 Red Flags
Explode 3 Bombs
Explode 5 Bombs
Explode 10 Bombs
Explode 15 Bombs
Disarm 3 Bombs
Disarm 5 Bombs
Disarm 10 Bombs
Disarm 15 Bombs
Explode 1 Barrel
Explode 5 Barrels