Blows himself up with enough force to destroy the Earth

"And I shall," the monster said, a hint more life in his words than before. "Right now." His voice was suddenly smooth, relaxed. "If I, myself, am not yet perfect, then that most certainly means I am finished. I am your second, Gohan. For all intents and purposes, you are far more perfect than I've ever been. You've beaten me! And I'm afraid I just can't allow that."

"Say what?" Gohan snapped, a golden orb of energy lighting up the center of his palm.

"Hehe!" the monster suddenly chuckled. "It's all over, boy!" He grinned as his body suddenly bulged like a balloon. Within an instant he was already swollen to three times his normal size. The purple segmented band around his waist was now more than three meters across, making him appear like a massively overgrown eggplant. But the energy swirling out from around him was sickeningly dark and sinister.

"Don't bother trying whatever you're about to do, Cell! I should have known better than to give you even a few last words, but I'm going to finish this right now!" The ball of ki just in front of Gohan's hand immediately quadrupled in size, continuing to swell by the second.

"I wouldn't be so rash, boy. Haha! Don't you understand? I'm going to blow myself up; if you touch me you'll only hasten your own death! Not even I can stop it at this point, haha! And thank you, by the way, for allowing me the precious few moments I needed to gather the energy to do this. Really, you made this all possible, boy."

"...What!?" Gohan gasped, wide eyed.

"No! It can't be!" Trunks yelled.

"Blow himself up?" gasped Tien. "But...Gohan had this in the bag! We were so close."

"How could he!?" Krillin added, alarmed. "Please tell me Gohan can find a way to stop this!"

"Well well well," the monster chuckled evilly. "Would you look at this. I'd say the Earth has about thirty seconds left before I blow it to atoms. Try to enjoy them, everyone." The whirlwind of energy swirling around Cell was increasing by the second, vibrating through the nearby air, causing grass and leaves to shake with all their might. The Z fighter's clothes whipped in the wind as they stared ahead in utter terror, their lives only seconds from ending.

...

Quickly, Goku vanished and reappeared beside the boy, resting his hand on Gohan's shoulder. He smiled at his son, a look that carried deep meaning. "You did all you could, Gohan, and I'm proud of you. But right now I can think of only one way to save the Earth."

Tears were filling his eyes, but Gohan suddenly felt a chill down his spine. If his dad could really save the Earth, why did he seem to be acting strange right now, like this was a goodbye?

"I've got to go now, son," he said, turning and waving to the other Z fighters. He then quickly put two fingers two his forehead and instant transmitted just in front of Cell.

"Huh!?" the monster suddenly frowned, his bulging face barely recognizable. "Goku? What are you doing!?"

Looking the monster dead in the eyes, Goku smiled. "I'm saving the Earth."

"NOO! WAIT!" Krillin yelled. "GOKU!"

"DAAAAD!"

With only seconds to spare before the explosion, the pair vanished into thin air.

...

ZIP.

To everyone's complete shock, Goku was standing in between them all.

- Bringer of Death Chapter 74

"Well?" the hero asked, curious. Everyone was still staring at him in shock.

"Goku!" shouted Krillin, the first to approach the Saiyan. "You did it, then? You beat Cell?"

"Well, actually he beat himself. I just moved him to a place where he couldn't hurt anyone else."

The tall Namekian, finally back on Earth, stood just beside Goku. Even he couldn't refrain from smiling. "That was quick thinking, Goku. How did you know what to do?"

"And—" Trunks interrupted, quite confused. "What exactly did you do?"

"Oh, right," the Saiyan said, scratching his chin. "You wouldn't know that about Namek, would you, Trunks?"

"Know what about Namek?"

"Well, during our battles back there, things got pretty crazy. Vegeta wasn't exactly on our side...I'm sure you remember how he was."

...

"Long story short," Piccolo interrupted, "I knew we were all going to die unless I did something quickly. So, using our last wish to Porunga, I asked the dragon to form a protective seal around Namek to prevent it from being destroyed. Today, Namek is essentially indestructible...at least, as far as we know. It can't be frozen or burned or moved or blown up."

"Oh, I think I get it now," Trunks smiled. "So that's where you took Cell?"

"Yep! I'll admit, I nearly forgot all about that particular wish. But when Cell kept talking about blowing up the Earth, I suddenly remembered. So I checked for Piccolo's energy signature really fast—it's lucky I took him there just a few days ago—and then I took Cell to there. He was alone, too, so I don't think any Nameks were hurt by the blast."

Piccolo, his face still mostly serious, nodded. "From what I've observed, explosions that detonate on Namek's surface are reflected out into space by the barrier. I'm sure the only one who got hit by that attack was Cell himself."

...

The ground had been blasted to a perfectly flat plain for hundreds of miles in every direction. A column of smoke and ash rose high into the upper atmosphere, forming a mushroom cloud as large as a small continent. Yet the wish to protect Namek had held; the planet's crust was undamaged and air currents were already starting to dissipate the ash cloud from the explosion. The cloud rose so high and so quickly that it rapidly reached the edge of space; its boilingly-hot gases escaping into the void harmlessly.

- Bringer of Death Chapter 75