In Mass Effect, Commander Shepard meets a brash Turian C-Sec agent named Garrus Vakarian during the hunt for Saren, the rogue Spectre. Garrus is recruited to the Commander's heroic team before long, and he's a perfect fit: he's tough, smart, plays by his own rules and wants to deliver justice at any cost. But he still has some growing up to do.
Garrus was born and raised on Palaven, the famed Turian homeworld, but butted heads with his strict, traditionalist father. Garrus' habit of making his own rules goes against the grain of Turian society, and his personal arc proves it. In particular, there are five scenes that show how Garrus grows up and evolves as a person.
Parting Ways With C-Sec
One of the first things Garrus does in the games is also one of the most significant -- and Garrus does it more than once. In 2183, Garrus was investigating Saren but kept hitting roadblocks and red tape. The frustrated Turian clashes with Executor Pallin, but then he meets Commander Shepard. Garrus sees a fresh opportunity with this rising-star human who isn't bound by C-Sec's rules or ancient galactic politics.
Garrus eagerly joins Shepard's team to pursue Saren on his own terms and becomes a vital part of Shepard's Spectre squad, hunting Saren across the galaxy. Garrus revels in the lack of red tape and oversight, and it leads him to formally quit C-Sec soon after Shepard's demise at the hands of the insidious Collectors.
Becoming Archangel
Garrus takes Shepard's death hard, but he doesn't let it be in vain. Inspired by the Commander's methods, Garrus quits C-Sec and journeys to the lawless, brutal space station Omega to become a heavily-armed vigilante who looks out for the innocent. He forms an elite and diverse squad with like-minded fellows, from a Salarian explosives expert to a Batarian hacker, earning the nickname "Archangel" for his hard work. He gains experience fighting the local Blue Suns, Blood Pack and Eclipse squads, and, for a time, Garrus makes a real difference. Then, tragedy strikes: his teammate Sidonis sells him out.
Facing Harkin/Fade
Garrus journeys to the Citadel and storms his way through its many wards with Shepard, desperate to find Sidonis and make him pay. Garrus gets a lead: an elite agent named Fade knows where to find Sidonis. Garrus and Shepard realize "Fade" is Harkin, a disgraced ex-agent of C-Sec and a human. Garrus, in his obsessive rage, beats Harkin half to death, but Shepard restrains him.
Shepard points out that C-Sec can handle Fade from here, and beating people to death is not what Shepard and Garrus are really about. Garrus gives a gruff response at the time, but there's little doubt that he takes Shepard's words to heart. If Garrus were to become a senseless thug, he'd be the very thing he swore to destroy as Archangel. He narrowly avoids falling into the darkness.
Forgiving Sidonis
Soon enough, Garrus gets a lead on Sidonis and lures the traitor into the open while preparing to snipe him in the Citadel's wards. Shepard is the bait, but instead of allowing Garrus to take the shot, Shepard can warn Sidonis about what is happening and block Garrus' aim. Shepard learns the truth -- that Sidonis had been under extreme duress to betray Garrus to his enemies, something he's been consumed with guilt and remorse over.
Shepard spares Sidonis' life and allows him to wander off, explaining all this to a seething Garrus. Once again, Garrus learns that vengeful brutality will not make him any happier or improve the galaxy. Instead, he realizes that understanding Sidonis' position and peacefully moving on is the best route to take. Garrus is in awe of Shepard's compassion and understanding; it's easy to pull a trigger, but not so easy to forgive someone who hurt you so badly.
The Citadel Sniping Contest
During the Reaper invasion of 2186, Garrus gets a fun idea: he flies himself and Shepard to an upper bridge in the Presidium, bringing two sniper rifles and plenty of empty bottles to shoot at. He wants a final showdown between him and the Commander, to see who is truly the best marksman.
On the surface, it looks like friendly competition, but in reality, Garrus is preparing himself to face death and wants some closure regarding his skills versus Shepard's before their potential demise at the hands of the Reapers. Garrus needs this one last question answered, and it shows that, despite his bravado and jokes, deep down he is afraid of what may come next.
Garrus wants to enjoy these last few good days with his true friends while he still can. He won't turn his back on his duty, but Garrus has also learned that there should be more to a Turian's life than duty and discipline. He gets his one last fun outing with Shepard out of the way before journeying to Reaper-occupied Earth to begin the final battle. To Garrus, his friendship with Shepard means more than all the military rules and doctrine of the entire Turian Hierarchy.