Gotta, gotta compelling protaganist? Yeah? Gotta obstacle for him to overcome? Huh? Gotta story brewing there? Working on, working on that for quite some time? Huh? Yeah, talking about that 3 years ago. Been working on that the whole time? Nice little narrative? Beginning, middle, and end? Some friends become enemies, some enemies become friends? At the end your main character is richer from the experience? Yeah? Yeah?
The interesting bit for me is 'friends become enemies and enemies become friends'. I've wrought human drama from this myself once or twice (Living Things was skewered through the middle by the relationship between Anais and Gary), but I've usually ensured that such changes in balance change back again at some point. Betrayal is rarely permanent, because there's usually a reason for it: a misapprehension, a loss of temper, a difference of opinion or belief - all of these things tend to be mitigated with time, a disruption of equilibirum, not a destruction.
This rule follows for friends. A friendship is mutable and flexible enough to allow for such occurrences, but also the springback. Familial or matrimonial betrayal, on the other hand, is different, because a promise is made - whether it be vows before whatever deity you favour, or the contract written by your genes before you even gained a consciousness.
I saw Thor the other day, and found myself just slightly unconvinced by the betrayal of Loki. Sure, he had his reasons - power-hunger and an inferiority complex - but Tom Hiddleston made him slightly too sympathetic, slightly too understandable. It was as if he were quite prepared to take it all back if someone would just give him a hug.
To betray one's blood in such a way should be momentous, permanent. It's not like pulling a girl you know your mate fancies. It's not fixable or explainable, it's just bad. Baddies should be bad, especially in a comic book movie. It's not meant to be edgy and contemporary, it's supposed to be a modern fable.
Small betrayals and small acts of revenge are the stuff of literature: but they hurt more, because while there's usually a reason, it's usually a bad one, one that could be refuted if the affected parties simply talked it out. Greater betrayals are the stuff of epics, the end of the line. They represent the moment when all other options have been exhausted, when the equilibrium has already been destroyed.
Some people don't know the difference, it's true. Some believe that any betrayal is irreversible, any revenge the final solution. Sometimes I do. All I can do, I find, is wait for the balance to swing back, for the truth to assert itself. Like gravity, one cannot escape the truth for long.