Devimon had infected Leomon with Touch of Evil attack, having Leomon attack the DigiDestined against his will. He was briefly freed from Devimon's control by Tai's Digivice to save Tai and Agumon by fighting Devimon. However, he was infected with another Touch of Evil attack and was under Devimon's control once more. He later appeared to attack Mimi and Izzy when they were in Centarumon's temple, but they drove him off with their Digivices. When ordered to kill TK and Patamon, he was infused with an additional eight black gears which increased his size and power and darkened his colour tone, subsequently being able to incapacitate the obstructive Garurumon and Greymon with his Fist of the Beast King attack. He was freed by Matt and Tai with their Digivices. When he was freed by the children, he aided them in the final battle with Devimon, but was defeated. When Ogremon decided to get revenge for Devimon's death, Leomon scared him away. He also aided in the building of a raft that the kids needed to get to the Server continent.
While the DigiDestined tried to save their world from Myotismon, the Dark Masters took over the Digital World. Leomon was among those who tried to fight back. After being exposed to the power of the DigiDestined's Digivices a few times when he was under the control of Devimon, he had inherited the ability to warp digivolve to his Mega form of SaberLeomon (skipping the ultimate stage). He rescued Mimi, Palmon, Joe, Gomamon and Ogremon from being found by MetalEtemon and took them to where Digitamamon's diner was. When MetalEtemon attacked, Leomon digivolved to SaberLeomon to fight him. He threw himself in front of an attack heading toward Mimi, being mortally injured in the process. Gomamon digivolved immediately to Zudomon and attacked with his hammer sparks but could not hurt MetalEtemon since his body was coated with Chrome Digizoid. However, when Zudomon then threw his hammer at him, it cracked his body because the hammer was also made of Chrome Digizoid. With his remaining strength, SaberLeomon punched his claw into the cracked wound, destroying MetalEtemon, but causing himself to revert to Leomon. As he died, Leomon made his peace with his arch-nemesis, Ogremon, and now waits to be reborn at Primary Village.
At some point after the events of Adventure, Leomon reborn and continued his fight with Ogremon.
Digimon Adventure tri.
SaberLeomon is Leomon's Mega Form. After being exposed to the light of the Digivices, Leomon gained the ability to evolve straight to his Mega form, SaberLeomon. He remained an ally, but admitted he couldn't quite control the ability to evolve. He was killed by MetalEtemon when he used up all his strength to jab his claws into MetalEtemon's wound. However, Ogremon said that the Village of Beginnings had been ruined by the Dark Masters, so Leomon could not be reconfigured, along with Chuumon, Whamon or Piximon.