Doublekill - Kill 2 enemies
Triplekill - Kill 3 enemies
Quadrakill - Kill 4 enemies
Pentakill  - Kill 5 enemies
Hexakill   - Kill 6 enemies

Killing Spree - Kill 3 enemies without dying
Rampage       - Kill 4 enemies without dying
Unstoppable   - Kill 5 enemies without dying
Dominating    - Kill 6 enemies without dying
Godlike       - Kill 7 enemies without dying
Legendary     - Kill 8 + enemies without dying
Shutdown      - Kill an enemy on a killing spree