Quote Originally Posted by Rater202 View Post
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Regardless of any possible in-story reasoning for that, I still find it annoying. :-)

Really, though, "Dragon Ball" was never a series where only training was enough to increase your power, all fighters were still held back by their natural abilities. For instance: after training in the Hyperbolic Time Chamber, Piccolo was powerful enough to impress Trunks, who by that point was strong enough to easily defeat Cell's second form; and yet, regardless of all his training, Goku's assessment was clear that he wasn't strong enough to even be a threat to Perfect Cell. Meanwhile, Gohan went from not-even-a-Super-Saiyan to strong-enough-to-easily-overpower-Perfect-Cell-if-he-releases-his-true-power with a single year of training.

(Or, to put it another way: Krillin can train however much he wants, he won't ever develop godly ki.)

Not only that, but the kind of training was always important - there's a reason why Goku's advancement in the earlier story arcs was always tied to the teachers he had, or why weighted clothing is barely mentioned at all since high-gravity training came into play.

So, maybe 17 had all the reason in the world to keep pushing himself past his limits - it's possible that being absorbed by Cell changed him that much. But he didn't have access to any of the training advantages any of the Z Fighters had, even if he somehow were an incredibly gifted fighter with the natural talent to reach such power levels.

But to reiterate: regardless of any possible in-story reasoning for that, I still find it annoying. :-)