During the first mission , Shepard pulls the rocket/nuke/special weapon McGuffin right out of his ass (not literally) and kills every reaper and other enemy in one shot, but none of your allies die, because they die in the beginning of the second mission when Shepard dares himself to open the airlocks on the Normandy... After that you play as an Elcor that's just opened shop in the Citadel, all you do is stand around and use QTEs to talk to customers who ask about stange furniture for 5 hours. Then at the very end. Legion arrives, because he cannot die (remember, he's got a piece of N7 armor on him) and kills Everyone because they want to ("he" is actually 1183 geths) it takes place in a cutscene that's an hour long and it's basically a movie. BUT! all that takes place off-screen. Then it's over and all that's left on the screen is glowing EA logo.