Normandy Crew vs Megatron (prime)
Commander Shepard and the party members from all three games, Vs the Transformers Prime incarnation of Megatron. The Normandy crew gets whatever canon weapons they can carry and are given detailed knowledge on all of megatrons weapons and abilities.
The fight takes place in a large junkyard and let's assume some of the cover can withstand at least 1 shot from Megatron before breaking.
This version for those who have forgotten YouTube video