DB Chapter 411
From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
"Cell, Brought to Bay" (追い詰められたセル, Oitsumerareta Seru; Literally meaning "Cell, Driven to the Wall") is chapter 411 of the Dragon Ball manga.
Cell can't believe he has so much power, while Vegeta states how the kid countered Cell's ridiculously huge Kamehameha with an even huger Kamehameha. Gohan just stands there smirking, and Goku yells at him to hurry up and finish Cell off. Gohan says, "Finish him already? Haha, it's still too soon, Father. I must make someone like him suffer more." Goku and Piccolo can't believe Gohan would say that. Cell prepares to regenerate, while Goku yells at Gohan that he must finish Cell since he's the only one who can. Gohan just smirks, as Cell's body returns to normal. Cell catches his breath, and then starts screaming, "DAMNIT!!!!!"
Cell bulks up so he's really huge and then lands with a mad grin on his face. He says there's no way he could possibly lose and swings at Gohan, but Gohan easily avoids it. He swings again, but Gohan backs off, then flies toward Cell again and kicks him in the face. Trunks notes that Cell is using the transformation that focuses too much on power and ignores speed, which he'd told Trunks was a mistake. Cell then gets a weird look on his face, before finally spitting up... No. 18! Because of this, Cell ends up turning back to his second form. Gohan thinks this is boring now, and Cell gets pissed and starts screaming. But then Cell starts to expand, getting really fat.