Note: Really Bioware's own fault for going on and on about how you can die if you screw things up in the second game. And one assumes the third, too. No ME2 characters since there's not much information. Sections in chronological order. Random alien culture/biology bits not from the game were made up.
I. Freedom
Discipline and control ruled Kaidan's life, and it was discipline alone that kept him moving despite the odds.
He forced himself to hold position as enemy fire pounded into his shields. The majority of the shots were absorbed by the barrier, but there were already fractures in his armor where some had gotten through.
The pistol in his hands was a pitiful sight compared to the pulse rifles of the geth, but it made no difference to the power of Kaidan's biotics.
It was the same power that had broken Vyrnnus' neck and driven Rahna away from him.
The power that he had to keep carefully held in check every moment, paying for it in headaches, pain, and sleepless nights.
The power that had saved his life, and the lives of his crewmates, time and time again.
Another geth fell, armor and synthetic tissue crumpling beneath sudden weight. Sharp pain in his abdomen told him he'd been hit, but he forced it down and concentrated on his assault. For the first time in years Kaidan didn't need to hold back, didn't need to worry about the consequences for himself or his opponents. There wouldn't be a headache tomorrow, and…
And he was, still, in control. It was no longer the wild reflex of a frightened teenager, but the carefully honed strength of an adult, that he was finally free to unleash against a worthy enemy, for a worthy cause.
Despite the pain, the threat of failure, and knowledge of what would happen anyway if he succeeded, for an exhilarating moment Kaidan felt like a kid again – a kid looking up at the stars, thinking about the adventures in the books and movies. Living those adventures.
As the last geth fell, he wondered for a moment if they, too, could be someday more than weapons, and chuckled. Some sentimental moron you are, Alenko, feeling sorry for a flashlight on legs...
But if there was anybody who could figure it out, it would be the commander and the crew of the finest ship the Alliance ever commissioned.
Because---
Kaidan smiled as a glint of light in the corner of his eye signaled the Normandy finally taking flight just as the timer reached zero.