The Legendary Fusiondramon, the most dreaded Metal Empire Digimon not related to SuperMechadramon, is definitely something to behold in terms of it's size. While nowhere near as large as Gaiamon, it is still several times larger than Jupiter in it's actual size, though it's size seen in most places is far smaller. Fusiondramon has a plasma reactor within it's chest that fuels it's entire body. While at first the idea of a combination of two Super Ultimates is good, it gets hindered because it is extremely heavy and slow, unlike the slightly more powerful SuperMechadramon. However, when battling in space, it shows the true power of it's multi-combination Chrome Digizoid armor. Having nearly all of the types of Chrome Digizoid forming it's body, it's unique in the fact it has all the traits of each type, but it's heavyweight body and gargantuan makes it slow either way in exchange for being nearly indestructible.
Digimon World: Aftermath
Fusiondramon is the final boss of the main storyline. In it's initial fight, it's much larger than it's obtainable variant for obvious reasons. It's attacks hit very hard, and it's defense allows it to take hits easily in addition to it's massive HP, but it is very sluggish, and you have the help of several allies helping you in the battle, but that's undermined by Fusiondramon's extremely high HP and Defense. It can be obtained only after having obtained Stellerdramon and Photondramon, which DNA Digivolve into Fusiondramon with the Fusion Core at Level 99.