SaiyajinPerfection

Vegetto in my opinion was probably using 20% of his power.....at the most:

He was only SSj when completely dominating Buu, and he most likely had the ability to SSj3 since Goku was able to.

And his base form was not filler; however, the fight in his base form was.

A zenkai of 100 fold is hard to imagine, but it also depends on the Saiyan's original strength, and how badly he (now let's not be exclusive: or she) is beaten. But of course Dragon Ball is inconsistent, Goku gets rediculous zenkais during the Saiyan and Freeza arcs; while Vegeta's zenkais, though notable, are on a much smaller scale.

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