Dragonball Xz, dark TRUNKS Saga, Episode 14 - "Right Back At Ya' - The Power of Dark Copy"
Goku goes Super Saiyan 3 again and charges at Super Dark Saiyan dark TRUNKS. dark TRUNKS proves to be more powerful than the Super Saiyan 3 form. Vegeta, Gohan, and Goten all get up and go Super Saiyan 2 again. All four of them fight dark TRUNKS at once, but dark TRUNKS has no problem taking on all four.
"I know how to deal with this worm," Vegeta says. "BIG BANG ATTACK!" Vegeta yells as he charges a Big Bang Attack. He fires it at dark TRUNKS and the others jump out of the way. It explodes and smoke covers dark TRUNKS. Then a black beam that looks exactly like the Big Bang Attack but black fires out of the smoke and devistates Vegeta.
"The hell?" Gohan asks as he charges his Masenko. "HAAAAAAAAAAA!" Gohan yells as he fires his Masenko at dark TRUNKS.
dark TRUNKS takes it head on and says, "Dark Copy." He then charges a black beam and exact same way Gohan charges his Masenko.
"Dark Masenko," dark TRUNKS says as he fires a black Masenko at Gohan. It takes him down in a single shot.
"What was that?" Goku asks.
"I got him, dad," Goten says as he charges a Kamehameha. "Kamehame--" Goten is interupted by Goku.
"Wait. He's copying our beams we use," Goku says.
"You got me. It's called the Dark Copy. I can use it to copy any beam you use and turn it into a dark version of itself. A dark version is a black version of the original beam, but it is exactly 10x stronger," dark TRUNKS says.
"Shit," Goku says.