This was it.
All that was running through Shepard's mind, he had come this far, and after everything he'd been through, this was finally it. The three choices the ghostly child had presented him with would all end in the destruction of the reapers. It was this close to being over...but there was one choice that remained.
Control? Like the Illusive Man? What would he do with the reapers, just send them back to dark space and never let them show themselves again? He didn't know, it overwhelmed his mind just to think about it. Look what happened when the Illusive Man tried to take control, would he end up like that? Control seemed too...wrong, controlling your enemy? He couldn't do it, it wasn't right, something didn't sit with him right in his gut when he considered it.
Slowly, he shifted his gaze to directly in front of him. The large beam of the crucible, glowing with the possibility of the final stage of evolution.
Synthesis. This seemed like the most reasonable option, combine synthetics and organics, but would that really end well? The final stage of evolution? He thought it seemed appealing, but it seemed too perfect. Shepard couldn't trust it, he knew deep down that ever since he'd found out about the reapers, he'd had only one goal. Destroy them. Stop them. Not control them or find a workaround.
End them.
And he was more than willing to pay the cost to end the reaper threat with his own life.
He slowly started down to the right, gun in hand, to destroy the reapers. He recalled memories of fighting Sovereign, and finally taking him down. The assault on the Collector base, losing close friends he'd lost so much. People, trust, friends, colonies, crewmates, even Anderson was dead now, the man who was with him and believed him from the start, it had all been taking a toll on Shepard for a very long time. Now, his life was going to end it all, it was going to act as the final note on a song of tragedy, except this note, while seeming bleak, would be slightly uplifted, higher, than all the others.
As he made his way towards the glass chamber housing all the wires, he raised his gun, firing, first just one shot, then firing several times into them as he continued walking towards it, each shot causing a spark. Slowly, in his mind, he saw a picture of Liara, he loved her, he loved her so much, and it broke his heart to be breaking every promise he made to her about coming back, and blue children, with every shot he fired, but he had to do it. The reapers had to be stopped. He only hoped whatever happened to her, she ended up happy.
Finally, as he reached the glass and fired a final shot, a huge explosion quickly followed, sending him crashing to the floor and scarring his flesh with burns as the flames consumed him, ending his life. Explosions rang out on the Citadel, the flames ate away at his skin, but he didn't cry out in pain or fear, he had known this day would come for a long time.
The ultimate sacrifice.
It was finally over.