To unlock this avatar award, you must kill 100 opponents in a row without dying in either Firefight or Campaign mode. To do this very easily, go to Firefight mode and select "Game Settings". Select "Spartan Settings" and go to "Shield Damage And Resistance". Set the "Shield Damage Resistance" to "Invulnerable". By doing this, you will never die, not matter what damage taken. Press B and go to the "Weapon" options. Set the "Infinite Ammo" option to "Bottomless Clip". By doing this, reloadable weapons never have to reload and plasma weapons never overheat. Start Firefight mode under any difficulty setting. You can kill 100 enemies in a row without dying easily. Once done, you will unlock an Avatar Award which contains JUN's helmet. You can use the helmet by going to "Customize Avatar" and selecting "Avatar Awards". Note: Doing the "Invincible trick" on Firefight too much may lead you to lose your actual skill.