Matadormon (Cyber Sleuth)

Matadormon is the one of the main antagonists of Digimon Story: Cyber Sleuth - Hacker's Memory.

Digimon Story: Cyber Sleuth - Hacker's Memory
Yu Nogi came across a mask whilst in Kowloon and put it on, which lead to him becoming K and stealing Keisuke Amasawa's account. As it turns out, the mask was a Matadormon in disguise and spent the entire time manipulating Yu into doing illegal things to get Keisuke's attention, instead of him always relying on Hudie. Eventually, Matadormon reveals himself when in "K's server" as being the one behind everything that has happened to Keisuke. Keisuke manages to defeat Matadormon - turning him back into a mask and freeing Yu - who still pities himself because he's still the little kid who would get bullied and have Keisuke rescue him.

GranDracmon
GranDracmon is Matadormon's Mega form. GranDracmon reappears in the Abyss Server.

After Keisuke saves the world, Mirei Mikagura informs him that an evil force has been found in the Abyss Server. Keisuke goes to investigate, finding a VenomMyotismon waiting for him. Venom states he will not allow Keisuke to interrupt his master's ritual and attacks, though Keisuke defeats the evil demon. After returning to Mirei, she states that she still senses evil even further in the server. After going through all 30 floors alongside one of the friends Keisuke made during his journey, they defeat bosses on floors 10 and 20 and then encounter GranDracmon on the final floor, who is extremely angry that he has to deal with Keisuke again. He explains that he plans to hold a ritual to obtain all of the power coursing through the Abyss Server and that will then make him immensely powerful and once acquiring said power, he will use it to take over both the Digital and Humans worlds, though Keisuke is able to defeat him before he gains the power to do so. After informing Mirei that he killed the evil demon, she thanks him though states that since he is a vampire, he has a very high chance of being reborn and that he should be careful. Upon returning to the 30th floor, GranDracmon has indeed revived, so Keisuke fights him again to stop his wicked scheme, only this time GranDracmon is even more powerful. Keisuke defeats him but this just ends up with GranDracmon reviving over and over again, getting more and more powerful every time he is slain.