Defeating Terrigon is similar to defeating Plasmus. The only difference is that he has an electronic barrier. To break the barrier, stand on a green platform that will temporally short-out the shield. It will not take long; be ready and already hold the barrel you will throw at him through the barrier. You probably will not have time to hit him with another barrel before the barrier returns. Repeat the process until the team is ready for the team attack. Unlike all the other times, the team's placement is not near one another; they will form a circle around Terrigon.