The training between an ODST and a Spartan is incredibly different... Both sport armor superior to that of a Marine, and they both have training to advance this and back up their position. Spartans are advanced super-soldiers, genetically modified and ODST are highly trained Marines, to be frank about it. ODST rely heavily on their group. They can kick ass on their own, but in a group, ODST are a deadly driving force in a battle. Spartans are especially dangerous when in groups, but they are initially trained to fight individually and rely on themselves rather than a unit. They are superior in strength, their armor is stronger, and the weapon choice will remain fair and even. 1 knife, 1 assault rifle with 252 rounds, 1 magnum with 60 rounds. This is standard issue, Marines can pack this much. A full squad of ODST can range around 6 on average. 6 ODST versus 1 Spartan, it is quite obvious that the ODST would win. It's the same for Grunts (Marines), Jackals (ODST), and Elites (Spartans). We won't get down to the Covenant level, but the question remains, a drop unit of ODST (Assuming there is 6 or more, as usual) vs. 1 Spartan. It is very likely that the Spartan will kill at least 1 or 2 ODST, but we must consider that Spartans have titanium armor, they are genetically modified with increased impulse and reaction timing and control. Spartans on instinct will easily kill half the ODST squad, no holding back. But the ODST, if piling onto the Spartan and just bashing, and forget the guns, just fists and knives. There is much to consider in fighting style + training. I personally prefer ODST and believe they would win no matter what. If there were 2 Spartans, it would be trouble for the ODST. This at least proves the UNSC did a good job of making a tank out of their frontline units. All in all, ODST win fair and square, and it is a near fair matchup to verse a squad of ODST and a Spartan. It is final, that ODST win, not easily though, they will face injuries and casualties, but ODST will pull through and beat the Spartan.

Yeah, but in Fall of Reach the teenage Spartans were able to overtake the ODST's. So, I would argue that a lone Spartan would still be victorious.