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I'm still thinking about this and I feel like it perfectly encapsulates who Garrus is and the nature of his relationship with Shepard (romanced or not). Throughout the entire trilogy, Garrus's defining character trait is loyalty: paragon or renegade, Garrus ALWAYS has your back. https://twitter.com/fiannan/status/1313789748675137536
I don't think I'm projecting or exaggerating when I say no one trusts Shepard more or has greater faith in them than Garrus. He's not above voicing his opinion or questioning Shepard's decisions at times, but ultimately he supports them no matter what (for good or ill).
During his recruitment conversation in ME2, when Shepard says "If I'm walking into hell, I want someone I trust at my side" Garrus replies "You do realise this plan has me walking into hell too, right? Hah. Just like old times." No doubt, no hesitation. Shepard needs him? Okay.
From the moment you recruit him in ME1, Garrus is willing to follow Shepard anywhere...even to hell and back. Aside from Tali (who joins your crew in ME2 & ME3 pretty late), he's the only squad member who's with you in all three games. I don't think that's a coincidence.
Anyway, all of this is why I think Garrus's line during that final goodbye at the beam totally fits his character as we know and love him: even injured and unable to stand on his own, he still wants to follow Shepard wherever they're going. "Till the end."
