Digimon Tamers - Season 1 Episode 34
Overview: As the gang meet up again they are quickly attacked by Beelzemon. However after Beelzemon kills Leomon, Takato, fueled by rage, forces Guilmon to Digivolve to his Mega Form – but it goes horribly wrong and Takato's D-3 Explodes, transforming Guilmon into the terrifying Megidramon.