The Legendary Super Saiyan Broly Z Ultimate Attack! Dragon Ball: Sparking! ZERO

Explanation of when Goku realises its the power trail he had been chasing: Broly appears to be a quiet and gentle Saiyan until his personality is later dispelled as a charade caused by the suppression of his ring. He accompanies Vegeta to planet Todokama, ironically in search of the Legendary Super Saiyan. When Goku appears at Paragus' palace after warping to New Vegeta using Instant Transmission, Broly starts to fill with rage at the sight of Goku, before his father finally manages to calm him down. However, that night, Broly fails to control himself and goes into a blind rage, attacking Goku in his suppressed Super Saiyan form. Eventually, Broly manages to power up significantly, with Goku upon his doing so recognizing it as the very same energy trail he had been following, and then promptly accuses Broly of being the one responsible for attacking the South Galaxy (in the FUNimation dub, he instead just demands that Broly listen to a newly arrived Paragus and calm down). The battle is drawn to an early close when Paragus arrives and is able to once again use his control over Broly. This encounter leaves Goku in surprise and certain that Broly is the Legendary Super Saiyan he has been tracking down.