Lantar Sidonis

Lantar Sidonis is a turian, whom Garrus Vakarian holds a grudge against for getting his squad killed.

Background
During Garrus' stint as "Archangel," Sidonis was one of Garrus' squad mates in the Terminus Systems. Sidonis betrayed his squad by selling information regarding their location to various mercenary groups, while giving Garrus a false lead. By the time Garrus discovered his dead teammates, Sidonis had already vanished.

Eye for an Eye
Garrus eventually learns of Sidonis' general whereabouts and that his disappearance was facilitated by someone called "Fade". Garrus then asks Commander Shepard to help him exact his revenge. Together, they discover that "Fade" is, in fact, the former C-Sec officer Harkin. After interrogating him, they force Harkin to arrange a meeting between Shepard and Sidonis. Garrus sets up a sniping position to assassinate Sidonis. Shepard has the choice to facilitate the assassination by leading Sidonis into Garrus' line of sight or warn Sidonis of his assassination attempt.

If Shepard helps Garrus, then Garrus will shoot Sidonis with a sniper rifle, killing him.

If Shepard chooses to warn Sidonis, it is revealed that he was under duress by the mercenary syndicates and only sold out the information to save his own life. As a result, Sidonis had suffered from survivor's guilt, eventually apologizing to Garrus via Shepard's communicator, and mentioning that he'll make it up to him somehow. It's later revealed in a news report on the Citadel that Sidonis turned himself in to C-Sec, confessing to the murders of Garrus' team. However, it is uncertain if he will be convicted, as the murders were committed on Omega and outside the Council's jurisdiction.

Trivia

 * In the mission Garrus: Eye for an Eye, if Shepard warns Sidonis of Garrus' assassination attempt and saves Sidonis, Sidonis will say, "You are a better man than I, Garrus." This may be a reference to the movie Gunga Din, in which it is said, "You are a better man than I, Gunga Din".

Lantar Sidonis