6x36 - Dragon Ball Z: Dragon Box

In order to buy enough time to let Trunks go back home and retrieve the Dragon Radar, Goku shows up to confront Majin Boo. To keep Babidi and Boo's attention focused on him, he displays the Super Saiyan levels that were used first to defeat Freeza, then Cell. He then increases his power even greater and transforms to become Super Saiyan 3! With this tremendous power, he attacks Boo and is more or less able to hold his own against him!!