I think it would all be better if you could just tell the demon child to stuff it and make use of that massive fleet you brought through the Charon relay with you. We’ve proven that they die, and relatively easily, be it bringing down their shields or hitting the firing chamber when it’s charging. they said over and over that there was no way to beat them conventianally, but there was, it just seemed hopeless because the galaxy was divided, once the impossible was accomplished defeating the Reapers was totally doable, especially with the experience gained against the Reaper on Rannoch.

My ending would be – Shep destroying the magic star child – only to realize it is harbinger in a guise to confuse Shep. Once destroyed, the Reapers become less resiliant and they go down quickly. War Assets would then determine who survives. For example, if Shep did not get the Geth to ally with the Quarians, the Quarians are
destroyed.

Now, depending on other things, Shep is either going to live or die…

If your romance is alive, he or she will bust into the room with the rest of the crew that are alive, and using Jack as an example:

Jack busts into the room – biotically brushing aside anyone in her way. She is bristling with biotic rage. She sees Shep. They speak, something sweet – she’s worried – he can’t leave her…too many people have left her.

1. Then he dies, she screams and consumes them both in some sort of biotic flash that throws the everyone else backwards. The citadel starts to unravel – people run.

OR

2. Then he “dies” – seemingly coughing out his last breath as he tells her he loves her and to be strong – she does the same bioticish thing – but there is a cut-scene at the end where she is standing on a beach somewhere – the sun is rising. She has her arms crossed looking worried. Then she hears a noise behind her, and Shep is stumbling out of a shuttle. She runs to him and they embrace – he says something smartass like “Told you not to worry”. She slaps him one, then they smile and kiss. The end.

See – THAT’S an ending.