Diaboromon is the secondary antagonist in Digimon: The Movie, the minor antagonist in the third season of Digimon Fusion, and the most powerful Virus-type Digimon in Digimon World 2, introduced as the antagonist of the film's second segment, replaced by Kokomon in the third act.
Diaboromon is a Mega class Digimon that was infected by a computer virus that formed a bug-like monster with lanky arms.
As Keramon, he is a blue bug-like creature with several tentacles and long arms and big hands.
As Infermon, he resembles a robotic spider.
As Armageddemon, he is similar to Infermon, but is colossal and dark. It has a massive, purple body with black armor covering its head, back, chest, and legs. It possesses 6 legs like that of an insect, with a long tail with a stinger a the end. The head is reptile-like, with two horns, wide jaws, and green eyes.
Digimon Adventures 01
Diaboromon first appears as a hatched Digi-Egg named Kuramon, he Digivolved to Tsumemon to eat the data, then he became Keramon. Agumon and Tentomon snuck up behind the virus, who is distracted by eating more data Agumon and Tentomon attacked him from behind, but Keramon then faces the two Digimon and fights back. Agumon and Tentomon became Greymon and Kabuterimon and took down Keramon with one shot, but after the attack he immediately digivolved to Infermon. Infermon then easily defeats Agumon and Tentomon in their Ultimate forms, and got the opportunity to escape and infect the entire network in the city.
Tai and Izzy were able to call Matt and T.K. for help, and their Digimon partners, Gabumon and Patamon came to the rescue. Agumon and Gabumon became WarGreymon and MetalGarurumon and attacked Infermon, then he Digivolved to his true form, Diaboromon. After Diaboromon defeats them, he disappeared and hacked into the military missle computer system and lauched 2 missles to blow up part of Japan and a state in the United States in 10 minutes. At the same time he multiplied up to over 75,000. When a weaken WarGreymon and MetalGarurumon went after the real Diaboromon they were easily defeated, and nearly killed by him. Believing they were about to die, Tai and Matt managed to enter the network and comfort their Digimon partners. They managed to gather enough strength and fused into the mighty all-powerful Omnimon for the first time. With their extra strength, Omnimon managed to destroy all the Diaboromon clones leaving only the real Diaboromon left. Knowing that Omnimon was too strong, he decided to leap around Omnimon with his great speed. Diaboromon was attempting to prevent them from disabling the missles, however, Izzy found out by sending the E-Mails it would slow down Diaboromon, and Izzy did just that. After he send the E-mail to Diaboromon, Diaboromon slowed down. With only 10 seconds left, Omnimon rushed in and stabbed Diaboromon in the head, killing him and disabled the explosion with only less than a second to spare. The much hated monster disintegrated, and all that remained of him was his watch. The remaining virus would soon infect Kokomon shortly.
Digimon Adventure (PSP)
In the PSP adaptation of Digimon Adventure, Diaboromon is the final boss of the Our War Game arc and arguably the final boss of the main game.
Digimon Adventures 02
Later in the sequel, Digimon Adventure 02: Revenge Of Diaboromon, Diaboromon survived and returned for revenge. He did this by creating an army of his offsprings; Kuramon. After he was defeated for the second time, his offsprings merged together with Diaboromon's data and became Armageddemon. He easily defeated Omnimon, and Imperialdramon. But When Omnimon fused with Imperialdramon Fighter Mode and became his Paladin Mode he was granted enough strength to destroy Diaboromon once and for all.
Digimon Fusion (season 3)
A random Diaboromon was created by Quartzmon that took the form of a Tsumemon. After Infermon was defeated by XrosUpArresterdramon (Astamon), Infermon digivolved with an army of Quartzmon and became Diaboromon. He was proven to be more than a match for the Digimon Hunters, able to defeat Arresterdramon, Astamon, Cho-Hakkaimon, Tuwarmon, and OmniShoutmon with ease. Diaboromon was about to kill Tagiru, but was shot by Beelzemon. Diaboromon was eventually destroyed by Shoutmon X7.
Digimon World 2
Diaboromon may appear at level 35 every 14 floors at Tera Domain alongside two lv. 5 Betamons. He can also be digivolved from an Okuwamon that has +20 DP.
The English Dub created the plotline that Willis from the third Digimon movie created Diaboromon in order to create a continuous storyline due to the first three movies being combined into a single film.
In the English dubbed version, Diaboromon is voiced by Paul St. Peter, who also voices fellow Digimon villain Apocalymon, Wormmon in Digimon Adventure 02, Cherubimon in Digimon Frontier, and Xemnas in the Kingdom Hearts series.
It is rumored that his name means "Diabolical Monster."
Although Diaboromon was killed off halfway to introduce the real main antagonist, Diaboromon served as the Heavy because it was the infection of the internet that drove the plot which made Kokomon the Big Bad because he was far more dangerous than the previous monster, and the one behind the plot.