This is the infamous Broly as a Super Saiyan 3. He only appears in the upcoming game for the PS3, DragonBall Z: Raging Blast.

Broly possesses the same wickedness as Kid Buu, who is by far the most evil and merciless being in the series. Even as a child, Broly was so dangerous that there were times he'd go berserk and start blasting everything he saw. This fact greatly contributes to his amazing power, since he has no regards for the well-being of others around him, thus going all out in a battle for feeling free - not caring if anyone nearby gets hurt. He is so cruel especially after assuming his Legendary Super Saiyan form that he even slaughtered his own father, Paragus, in front of the Z-Fighters just to satisfy himself as well as to demonstrate his own brutality.

Even at birth, Broly's power was amazingly high. His power also grew as he grew up, and he didn't train as much as Vegeta and Goku did to increase his strength. His transformation, the Legendary Super Saiyan, is an exclusive transformation that places Broly in the league of his own. It is way superior to an ordinary Super Saiyan form that it almost matches Super Saiyan 2 in strength and power, if not in speed. This transformation corresponds to Trunks' and Goku's Ultra Super Saiyan, but it's much stronger. There are two major differences between Broly's Legendary Super Saiyan form and the Ultra Super Saiyan. In Legendary SSJ form, Broly doesn't lose a lot of speed and his energy will keep rising for as long as he remains in the form, as opposed to the Ultra Super Saiyan who loses energy just by trying to maintain the form. In other words, Broly's transformation provides him with virtually unlimited supply of energy, similar to the Androids. In this form, he easily took care of Goku's Full-Power Super Saiyan, who was fighting evenly with Perfect Cell, suggesting that Broly's power is superior to Cell's. He also defeated Piccolo's Super Namek form, Trunks' and Vegeta's Ascended forms, and Gohan's Full-Power form together without much effort. What would Broly's power be like in his SSJ3 form?

In Broly's SSJ3 form, his power would greatly exceed SSJ3 Goku's. He'd most likely overtake Buuhan(Mystic Buu) as the ultimate villain in Dragon Ball Z. His power would probably approach Gogeta's SSJ form and Vegito's base form.

Just imagine if Broly did not die and became one of the good guys like Vegeta did, then he would be the strongest Z-Fighter in Dragon Ball GT.