Abbadomon

Abbadomon is an Unidentified Digimon. It is a mysterious Digimon that digivolved enormously by absorbing the negative data that the Network is overflowing with beyond its limit. Its raison d'être is to transcend good and evil, and return everything to nothingness. It bites into Digimon and the Digital World itself with the large mouth at its center and the mouths on its numerous tentacles, and after doing so, only the blank data of empty space is left behind. The birth of Abbadomon is undoubtedly a crisis for all Digital Worlds, so it is conjectured that some Digital Worlds from other dimensions have been annihilated by it. You will be erased the instant you suffer any of Abbadomon attacks.

(Source: Digimon Wiki)