I feel like people are going to be eating their words by the end of the season. Telltale really hasn’t made a cast-character that has been 100% irredeemable or dislikable. Even the St. Johns, Nate and Carver could be understood and empathized with, even if they’re disliked in general and have made some pretty unforgivable choices. Even Troy is given a moment of vulnerability before Jane shoots him, and damn near all of his canon characterization was creepy-ass child-abuser.
My guess, knowing next to nothing about Arvo and his crew yet, is that he’s running with this crowd because they keep him (and, if he’s telling even a little bit of truth, which I’m still on the fence about) safe. But nothing comes for free. The others in that group are strong, well-armed and appear ruthless. Arvo appears skinny and weak and easily startled. My guess is that they use him as an errand boy, and that he does what he does because he feels he has no other choice.
I’m willing to bet Arvo is the one who helps Clem and the surviving cast escape the situation they find themselves in after the shootout. I’m willing to bet that, regardless of you stealing his supplies, he will help you because you have a baby and it’s his fault you (likely) lose some of your group in the shooting. My prediction is that in return he’ll ask you to take him (and, if she exists, his sister) with you, but that his injury will prevent him from escaping, and he won’t be among the final surviving cast.
Sorry, walker!Lee. Looks like you’re gonna miss another meal, trapped on that radiator. Poor old Lee.