In a match, allow your opponent to build up a gamebreaker meter. Once they have, and they access the Gamebreaker, you’re going to have to steal the ball from them and score.
This is typically harder than a normal goal, because while a user has GB activated, their whole team becomes “SUPER-TEAM”, which means a whole new set of animations and abilities for each player on the team. Once you score, their GB activation will be gone. This can be rather time consuming, as the AI opponent will sometimes take a while to build up their Gamebreaker Meter. It would be best to obtain this one in a Gamebreaker match, where the AI is more likely to build up their meter than usual.
Use a second controller, build up the gamebreaker with controller 2, and give the ball back to their own goalie, access gamebreaker. Then drop the ball, and let yourself steal it and score it.