The Society by Lilith Saintcrow

The black-ops government agency called Sigma broke Justin Delgado, trained his psionic talent and turned him into a killer. Then he escaped and joined the Society, an underground resistance movement of psions determined to use their talents to bring Sigma down. Competent, cold, and cruelly efficient, he's the best operative the Society has, a legend among the psions who fight a shadow war against an enemy that owns the courts, the press, and the police. Feared even by his own teammates, hunted by the government, and too damaged to feel anything but clinical rage, he is utterly alone-until he meets Rowan.