I think it should've gone like this:
Admiral Hackett informs you towards the end of the game that the Reapers have figured out the Crucible is going to destroy all reapers no matter where they are in the galaxy using the mass relays. He informs you that through a leak on your ship that they also have figured out the Catalyst is the only thing they need to stop that and so they take the Citadel (which they've heard houses the Catalyst) to earth and gathered every Reaper in the galaxy around Earth to protect it. Then, having only one move left, Shepard gathers every ally he/she's found and you begin a frontal assault. Then, surprisingly, the Normandy leaves formation several minutes early, but the rest of the fleet is ordered to stay behind.
You arrive through the relay to see about ten bazillion reapers huddled around earth. Instead of destroying you instantly, Harbinger comes forward to stare down your ship. He then opens a hailing frequency and you begin to talk. Shepard calls the entire crew to the cockpit to talk to the Reaper. It's here that Harbinger starts taunting Shepard, lots of "This hurts you" and "Your resistance is futile". Shepard shrugs it off, but then Harbinger reveals something shocking! The leak on your ship is your romantic interest (whoever that may be) and they've been indoctrinated since ME1. Then he says that the betrayal will cost you the war and laughs, if Reapers can laugh.
Then Shepard, probably drinking a BIG GULP full of brandy, begins laughing too. He/She then reveals that he/she knew their love interest was indoctrinated and used them to feed the reapers faulty intel. Shepard reveals that there is no such thing as the Crucible or the Catalyst. It was all a scheme by the Alliance to get the Reapers to capture the Citadel. Why? Because there was something on the Citadel. THE BIGGEST EMP EVER! Shepard detonates it remotely with one of those comical plunger detonators and all electronics in the solar system go offline for 15 minutes(but the mass effect relays don't for some reason). Then the alliance fleet moves in right on time, missing the blast. The ships, encountering no resistance from the offline Reapers, tear the Reaper fleet apart. 15 minutes later the Normandy boots back up, EDI may be lost during the EMP (maybe you can save her with enough war assets) and not a person is killed because the Reapers couldn't even fight back. Your love interest is saved because there are no longer Reapers to control them, everyone on earth has to buy new iPads, the Illusive man says he super sorry and everyone lives happily ever after. Also Kai Leng doesn't happen. Like, at all. Just isn't in the game. THE END
Admiral Hackett informs you towards the end of the game that the Reapers have figured out the Crucible is going to destroy all reapers no matter where they are in the galaxy using the mass relays. He informs you that through a leak on your ship that they also have figured out the Catalyst is the only thing they need to stop that and so they take the Citadel (which they've heard houses the Catalyst) to earth and gathered every Reaper in the galaxy around Earth to protect it. Then, having only one move left, Shepard gathers every ally he/she's found and you begin a frontal assault. Then, surprisingly, the Normandy leaves formation several minutes early, but the rest of the fleet is ordered to stay behind.
You arrive through the relay to see about ten bazillion reapers huddled around earth. Instead of destroying you instantly, Harbinger comes forward to stare down your ship. He then opens a hailing frequency and you begin to talk. Shepard calls the entire crew to the cockpit to talk to the Reaper. It's here that Harbinger starts taunting Shepard, lots of "This hurts you" and "Your resistance is futile". Shepard shrugs it off, but then Harbinger reveals something shocking! The leak on your ship is your romantic interest (whoever that may be) and they've been indoctrinated since ME1. Then he says that the betrayal will cost you the war and laughs, if Reapers can laugh.
Then Shepard, probably drinking a BIG GULP full of brandy, begins laughing too. He/She then reveals that he/she knew their love interest was indoctrinated and used them to feed the reapers faulty intel. Shepard reveals that there is no such thing as the Crucible or the Catalyst. It was all a scheme by the Alliance to get the Reapers to capture the Citadel. Why? Because there was something on the Citadel. THE BIGGEST EMP EVER! Shepard detonates it remotely with one of those comical plunger detonators and all electronics in the solar system go offline for 15 minutes(but the mass effect relays don't for some reason). Then the alliance fleet moves in right on time, missing the blast. The ships, encountering no resistance from the offline Reapers, tear the Reaper fleet apart. 15 minutes later the Normandy boots back up, EDI may be lost during the EMP (maybe you can save her with enough war assets) and not a person is killed because the Reapers couldn't even fight back. Your love interest is saved because there are no longer Reapers to control them, everyone on earth has to buy new iPads, the Illusive man says he super sorry and everyone lives happily ever after. Also Kai Leng doesn't happen. Like, at all. Just isn't in the game. THE END