Arkadimon(mega), ChaosGallantmon and Chaosdramon.
Grimmon becomes ChaosGrimmon when he absorbs the all of the Pockets (including the Dark Area). All of the Tamers Mega's attack at the same time and defeat him. He retreats towards Infinitydramon, and then eats him! This causes him to turn into ExoGrimmon. He degenerates all of the digimon and they turn into their fresh forms. Then the Digi-Team appear and DNA digivolve into UltimateKhaosmon, but they still can't defeat him. Then Xavier appears with Butenmon and they Biomerge to ChronomonHeroMode, and he destroys ExoGrimmon with one attack. This creates a black hole which absorbs Chronomon, turning him into his Destroyer Mode. This causes him to go berserk and he starts destroying reality. A wormhole appears and Chronomon heads to the human world. The Royal Knights try to stop him but he deletes all 13 of them in one attack. Their data forms into OmnimonX and he manages to subdue Chronomon, but sacrifices himself. While ChronomonDM is weaker UltimateKhaosmon destroys him, turning him into a Digi-Egg which Xavier catches. The last fragments of ExoGrimmon's data go into ChaosGallantmon (in his reincarnated Guilmon(data) form) creating Parallelmon. He then reopens the Digital World and starts absorbing it. The tamers talk to him and his Guilmon side comes out and instead of Parallelmon eating the Digital World, he recreates it by turning into Infinitydramon.