chief carrys around a 1ton or 1 cubic ton (i beleive cubic is 1k lb right??) and can jump higher, run faster, and it harder than any human being.
and tbh, it depends on what kind of fight theyd do. if its a fist fight, MC hands down. hed just run up to him and knock his skull out of his brain, them beat him with it (rvb reference "this doesnt seem physically possible!!!" lol soi soi soi)
if weapons, then depends on what you gave them. halo 3 weapons, mc hands down again. gow, prolly marcus cause he knows those and chief doesnt. both, mc hands down. spartans are trained to be able to pick up any wepaon on the field and use it for their own weapon, no matter whose it is.
btw, MC is like 7-8' tall, so i think hed prolly tower over fenix.
either way, i think chief would win...
btw laguna, 458 doesnt exist. unless he was in the Spartan I program. Spartan II went from 001-170 i believe (not sure) so spartan 071 (i dont remember his name, but i found him on this site) would just come and help mc kill him (acording to this halopedia page, he never did die...so >->