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One of the last episodes of Dragon Ball Super raised me this question.
Trunks fights alongside Goku against Black and Zamazu in Super Saiyan 2 state. But how strong he really is? In the fight Goku is Super Saiyan Blue and black Super Saiyan Rose, but he is able to score some succesful punches/attacks to Black and Zamazu, even though it doesn't hurt them. At the beginning of his appearance in Dragon Ball Super he is shown to fight Dabura. Later he is knocked in a training match against Goku Super Saiyan 3 (did he have a zenkai boost there?), and later he is knocked by Vegeta when training with him in Super Saiyan Blue (did he have another zenkai boost there?). And I've heard that in the manga he's a match for Goku in Super Saiyan 3, plus some mental training he has made since his appearance. Is Trunks now stronger than a Super Saiyan 2, may be at the level of a Super Saiyan 3? Or is he fighting alongside Blue and Rose super saiyajins just a plot-hole? We've seen a super saiyan 2 can be at the level of a super saiyan 3 already when Beerus tell to Vegeta that he made he uses more of his power in his fight (1% he says) than Goku in Super Saiyan 3.