8 Pairs, Nowhere to Run
There's only one race in the galaxy that is purpose-built, primed, and ready to unleash pure ownage on some bitches. The Krogan. Other races value things like stealth, or subtlety, not getting shot in cover, or tech bursts. Krogans value one thing: letting their enemies know exactly who is killing them, as they are headbutted to death.
Rules
Map: Firebase Giant
Enemy: Any (Reapers = :suicide: )
Difficulty: Gold
Characters: All four characters must play a Krogan. It doesn't matter how they're specialized, because all Krogans are badasses.