A) The Vex literally want to rule over everything in every dimension and possible timeline. Think robo-hitler. B) The Cabal are space-romans that attacked us without us aggravating them plus they at least one entire race, what's to say that they won't enslave us. Our fight seems pretty just to ms. C) The Fallen are good guys, we just don't understand each other ;-; And finally the Hive. [b]They literally want to kill everything that can be killed so that they are the only thing left in the universe.[/b] they believe that if something can be killed it does not deserve to exist so they go around destroying everything they see. Think space-kindergardeners. Terrifying. Our fight seems pretty damn just to me