You will fight Lewis, a boss at the end of Stage 5.
For this trophy, you have to counter 10 of his attacks. During the first phase of the boss fight, he will be on his bike, occasionally riding back towards you and attack you by swinging his guitar. This isnt to be confused when with when he dashes as you across the map. The only time you can counter him is when he rides at you at a slightly slower pace. Simply block his attack with Triangle Button, then mash it to counter back and win the duel. Repeat this 9 more times to unlock the trophy.
This trophy, along with other number specific trophies, is cumulative; you don't need to counter 10 of his attacks in one battle.