Hold on, why are we so focused on who would win? Why don't we think about how -blam!-ing badass it would be if Chief and the guardians teamed up. Imagine MC riding on a mother-blam!-ing sparrow (His suit would probably crush it tbh, but who the -blam!- cares, let's give the sparrows some plot armor and plot strength so they can hold and go fast with MC) Chief wielding a ghallarhorn and then pulling out a spartan laser on Crota and Atheon. God my balls would grow ten times bigger because of how manly and awesome chief and the guardians teaming up would be