Unlock invincibility! Go to the "\\25 to life\\data\\var" folder and open the "easy.var" file in your text editor. Note that you have to uncheck the read-only attribute first. Next, find the "AI2PlayerDamage 0.14" line and replace the "0.14" value by "0.00". That’s it!
Unlock Beatdown bonus level! Successfully complete twelve levels and mission objectives.