User blog comment:Gruntburner/Mass Effect 3 Achievements Revealed/@comment-4118072-20120204224838/@comment-3228423-20120208125116

I'm going with either TIM or the more likely Kai Leng. They both took the N7 training, no idea if it was at the same time, and they probably formed a less-than-friendly rivalry due to differing views if they had.