Angemon debuted when Patamon Digivolved into him in order to stop the giant Devimon. Not only did Angemon killed Devimon, but sacrificed himself by using up all the energy he had and reverted into a Digi-Egg where he was once reborn as Poyomon.
Angemon then returned to rescue WereGarurumon from Myotismon's Crimson Lightning attack and helped WereGarurumon fight Myotismon for sending Gotsumon and Pumpkinmon back to the Digital World.
During the showdown with Myotismon, Patamon Digivolved to Angemon once again and easily damaged Myotismon as well as killing Phantomon with a mere brush of his Hand of Fate attack.
After Myotismon was defeated and returned as VenomMyotismon, Angemon and Angewomon fought the giant monster while Izzy worked up a miracle to allow Agumon and Gabumon become their Mega Level forms.
During the Dark Masters arc, T.K. and Kari tried to be brave to escape from Piedmon, the last of the Dark Masters. Patamon became Angemon and distracted Piedmon while T.K. and Kari attempted to escape. However, Piedmon easily defeated Angemon and sliced the rope, sending T.K. and Kari falling to their doom. Angemon Digivolved to MagnaAngemon and saved T.K. and Kari.