'Shepard did everything right' - Miranda Lawson, ME2. If there's one thing that shat me about the ending, it's that I kept hearing that line over and over in my head. 'I did everything right, I united the galaxy, I have everything down to and including toddlers with BB guns aimed at these damn things and now it's all for nothing? I can end this not through my own herculean actions, but purely because it amuses the Starchild to do so? Suspension of disbelief = shattered.'
Whilst I can appreciate the need to have a 'bittersweet' (You keep using that word, Mr. Hudson, I do not think it means what you think it means.) ending to the story, and more importantly, tie off Shepard's story, I didn't think it needed to be SO bleak, or be solved by Deus Ex Machina.
What I would do = Retcon the damn Starchild. Turn the crucible back into a giant (nonsentient) can of reaper-b-gone. TIM dies, you and Anderson have your bro moment, Anderson dies, Hackett does his 'y my weapon no werk' transmission. Shep crawls over and does the 'I can't... It's not here...' thing. And HERE's where your choices matter.
1)If you completely fucked your war assets, Shepard dies against that control panel. A valiant attempt, but not enough.
You see cutscenes of your various forces, including the normandy crew, being crushed one by one.
Harbinger rounds on the normandy, Joker is sitting in the cockpit, teeth clenched as he goes for one last shot.
Harbinger speaks. "You have proven surprisingly resiliant. But you have failed, as we said you would have. Embrace your destruction."
Boom goes the Normandy, Reapers win, cycle continues, better luck in 50k years.
2)If you got a reasonable amount of war assets, but short of <arbitrary_value.cls>, you see the majority of your crew/forces getting smashed, but one eventually manages to transmit something like "SHEPARD! We're not giving up on you, don't you give up on us!" Which galvanizes Shep to pull himself up on the panel.
By chance he hits a switch which causes a device similar to a prothean beacon to extend from the centre of the panel. WHAM! Brain scramble time.
Billions of calculations run across shep's eyes as the Catalyst uses Shepard's brain to calculate a firing solution.
A final pulse knocks him away from the beacon and he hits the floor with a sickening thud. Through eyes beginning to drift closed, he sees the energy-pulse building in the citadel arms, then releasing with a silent concussion.
As it hits the first reaper, he smiles slightly, seeming to relax as it seems to implode into component compounds. Cut to earth, some buildings are damaged by the pulse, lots of people killed by the shockwave. Cut back to Shep, as he breathes his last. "We did it", he whispers, before collapsing into death. Fade to black.
Fade back up to a salvage team entering the room with the bodies of you and Anderson. If you have an LI who was not killed during the battle or in ME2, they are with this team. They react to your body in an appropriate fashion for their character. IE Tali is a crying mess, Jack is swearing through the tears, Garrus does a Saren-esque turian roar and scoops your lifeless form to him, etc. If Kahlee Sanders was rescued from Grissom, she similarly reacts to Anderson, whispering "I told you to stay alive".
There is a memorial service on Normandy/Arcturus/Citadel/whatever. Admiral Hackett is reading a eulogy about sacrifice and unity and all that other awesome moving shit. The camera pans out to show all of your surviving squaddies, the council, and a few other (random?) NPCs who you interacted with. Your coffin is lowered into what seems to be a grave, the camera then pans out to show the exterior space view. A puff of crystalized air is seen from the ship as your coffin sails out towards the Mass Relay, the arc hits it, and your body hurtles off into the unknown...
3) Your EMS is Golden - Similar to 2, though your troops are clearly owning ass. Triumphant music sounds as we see our Krogan smashing through brutes, Asari Commandos ripping Banshees apart, and Rachni zergrushing across the field, their song loud and clear... One of your squaddies (I see Garrus because he's the penultimate bro) radios up to Shepard, "We've got them held here Shepard, now finish these bastards off!". Once again, Shep pulls himself up, Beacon Brainfry, pulse heads out, we see Harbinger RUNNING LIKE A ***** towards the mass relay going 'NO! THIS CANNOT BE!' as we hear fear in a Reaper's voice for the first time. Joker's hot on his ass, Thanix Cannon and Crucible pulse hit simultaneously, Blowing Harbinger to shit.
This time, when the salvage crew come through, your eyes crack open when your LI enters, you get the 'At least I got to see you one last time' opportunity for a bit more closing dialogue... Maybe Liara/Ash/Jack admit they're pregnant or something... (sorry talimancers, your waifu is still a dextro) Either way, you die in their arms, it's all very moving. Roll eulogy, Coffin through the relay, credits.
In 2 and 3 your surviving squaddies get a short text epilogue outlining what they did afterwards during the credits, as do the major players (IE, how your actions affected the major races and what they had to do to rebuild/lol extinct).
And THAT, Mr Hudson, is how you do a motherfucking A B C ending without it looking like one.