This trophy is titled "Ride the Icening" and it's for using Jin's Musou Senshouzan or Tosshougeki over 20 times in one round and winning the round after. While the names are a mouth-full, you simply have to use the move where he glides across the map on an ice sword 20 times. Personally, I jumped up and rode the ice over the head of my second controller so it could be done relatively easily without harming the opponent ensuring you could do this in one round. If facing the AI, simply use this move as a means of getting some distance between you two and you should be fine. Naturally, it's easier with a friend or second controller. The trophy should unlock at the end of the round or towards the beginning of the next one.