Future Spock was so afraid of Khan, he broke his vow not to interfere.
Khan wins based of a few feats.
Able to steal transwarp capability and get it off planet onto klingon world.
Able to locate and infiltrate secret fleet project and destroy it via manipulation.
Ambush starfleet by knowing its protocols based on setting them all up and knowing where to go and what to do.
Was actually consulted by starfleet for help because of his advanced knowledge.
Many more etc, etc
Khan wins.