Chief without the benefits of his armor accidentally killed one of his corpsmen (with three punches) during a sparring drill - three combat trainers were also accidentally killed in the same day trying to train the other Spartans. He also lashed out with a straight kick, also without armor, and completely owned another soldier wearing external armor (think Mech, only much smaller) and ruined the exoskeleton in the process.
Chief has been around combat situations and has been registered as a professional soldier (and have been continuously training since) as early as the age of six. He has been trained extensively in numerous forms of close combat since then.
Yeah, Chief wins. By a curbstomp.