While 2.0 has a direct background plot in itself, there are several character arcs that are present within the series rather than focusing on only one.
Marcus' arc is the first introduced, being that he is the main protagonist. His story follows his struggle dealing with his father Adam being deployed constantly, and how he prioritizes his studies more than Marcus. Just when he learns Adam is being deployed once again, his mother Elain disappears where he is then inspired by Carlos to join the project along with Dom.
After Marcus and his friends are recruited, Marcus has to face hardship of his father being disappointed in him, and encouraging Dom to pull through after he is separated from Carlos. Marcus then is burdened by the fact that Elain is dead, and has to stand up for himself once and for all.
Dom's arc is secondary, and introduced when Marcus comes to visit after having a talk with Adam; the last day he sees Elain alive. Dom primarily joins the project on the sole fact that Carlos and Marcus had joined, and didn't want to be alone. Under the impression that the three would be together as self-proclaimed brothers, Carlos is separated into a higher level group where Dom is torn over it throughout most of the film.
After Dom learns that Carlos had died while fighting on a bridge in combat, Dom runs away where he is then comforted by Marcus, and realizes that they are all brothers to the end.
Baird's arc begins when he meets Cole after arriving on base where the two introduce each other and become friends. Baird mentions how his parents made him join, and that Cole joined because he wanted to help. Baird secretly admires that, and strives to impress him by befriending the Chevy Brothers to try and be cool.
After meeting Marcus and Dom, Baird invites them to eat with them at lunch and reveals his plans to make a clubhouse known as the Sugar Shack, to be a place where "all the cool kids" can hang out. The plan ultimately backfires after Morgan and the Chevy Brothers get alcohol involved, as fights break out and Cole wants no part of it. After discussing with Marcus what had happened, he realizes who his true friends are and returns to be at Cole's side.
Hoffman's arc begins after enlistment, where he is assigned by LT Anderson to be in charge of Delta where he requests Anderson's assistance. Hoffman goes through an emotional identity crisis, where he wishes that Anderson felt mutually of him instead of arguing with him, and is often pushing others away with his scathing remarks. Hoffman loses faith in nearly everyone, and eventually becomes overwhelmed after Anderson's death to the point of a mental assault. During his flashbacks, he realizes that he is not who he thought he was, and is in fact inhuman and incapable of retaining human relationships.
Anderson's arc begins shortly after Hoffman's where the two are discussing personal issues, where Anderson mentions he misses his dead wife and son who both died at the same time. Due to being caught up in his grieving, he is unaware of Hoffman's apparent feelings for him which pushes Hoffman to the edge, resulting in a faulty and toxic friendship.
When Anderson is shot and bleeding out on the aircraft, he tells Hoffman to take care of the children and jumps to his death, where Hoffman is angry with himself that he never confessed his feelings upfront.
The Chevy Brothers' Arc
The Chevy Brothers' arc is minor, yet crucial to character development in the story of 2.0 as the serve primarily as antiheroes. Coming from a rough background of a dysfunctional and alcoholic mother, and three separate dads in a household of prostitution, the Chevy Brothers are relentless and create an uprising of infamy with several members of the project.
Because of their nature, they lose more friends than gain. By the end of the film, Alex, the eldest brother tells his two younger siblings that everyone needs to work as a team, and that they have other "brothers" here (referring to Marcus, Dom, and the others) which redeems forgiveness. Despite all of this, the last living Chevy brother ends up being Niko, the least aggressive.