SkullGreymon

Technically the first ever Ultimate digimon owned by a DigiDestined, this digimon was the result of Agumon digivolving for the wrong reasons. This digimon was uncontrollable and the only good that came from this is it show the Digi-Destined not to misuse the power of their crests. later appeared in Season 2. His attacks are Dark Shot and Double Dark Shot.

Digimon Adventure
When Tai wanted Greymon to digivolve against Etemon's Greymon, it caused Greymon to Digivolve into SkullGreymon and easily defeated it. It also attacked Birdramon, Garurumon, and Kabuterimon before reverting back to Koromon.

Digimon 02
When the Digimon Emperor took over Greymon with a Dark Ring, he wanted him to Digivolve into MetalGreymon, but it instead turned into SkullGreymon defeating the Meramon, Flamedramon, Halsemon, Digmon, and a bunch of DarkTyrannomon before reverting back to Agumon as the Digimon Emperor makes off with him. No matter how much he tried to get Greymon to Digivolve into MetalGreymon, he turned into SkullGreymon until Agumon's recapture and the introduction of the Dark Spiral turned Agumon into a virus version of MetalGreymon.

Digimon Tamers
A SkullGreymon was among the many Digimon seen through the rip in the sky during Vikaralamon's rampage.