Buy any cat upgrade.
Complete level 7.
Complete level 6.
Complete level 5.
Kill 750 enemies.
Preform an UltraViolence kill combo.
Complete level 4.
Kill 500 enemies.
Complete level 3.
Kill 250 enemies.
Complete level 2.
Kill 100 enemies.
Complete level 1.
Kill 50 enemies.
Preform a Deadly kill combo.
Kill 25 enemies.
Preform a Brutal kill combos.
Preform a Cruel kill combo.