User blog comment:B214/Volume 23 discussion blog/@comment-30924344-20170319035400/@comment-29963364-20170319074757

@Omega64

Ddraig said that if Issei used Dragon Deitification (full power  DxD G  from vol.20 and 21), he could give Crom a good (close?) fight.

But if he used "pseudo" Dragon Deitification (the nerfed version that he used during the match with Baraqiel), he wouldn't stand a chance.

Not only that, but Issei can only use the "pseudo" DxD for a short time, and he can only unleash a full-powered attack once or twice before he runs out of power/stamina.

So the side-effects of DxD (full power) are still there. It's the "pseudo" DxD that Issei can use without the nasty side-effects. It's just not as powerful.