This trophy requires you to win the season championship.
Once you load into the game and are in the lobby, press on the "Play" button, navigate towards "CUSTOM GAMES" and press it. Choose "SEASON" and press "START NEW SEASON". I would recommend putting the settings like this:
Team Size: 1v1
Difficulty: Rookie
Season Length: 9 Weeks
Playoffs Teams: 4 Teams
Although you can choose your own settings, these are the ones that I highly suggest you put on as they make it so you'll only have to do 11 rounds and makes it really easy to accomplish.
Press "CONTINUE" to move on. The rounds will take 5 minutes long so if you do 5 * 11 it will only take around 55 minutes.
WARNING: YOU MUST WIN THE PLAYOFFS OR YOU WILL NOT GET THE TROPHY
After 11 matches of constant winning, you will unlock: Champion