Dark Evolution

Dark Evolution (暗黒進化 Ankoku Shinka, ダーク進化 Dāku Shinka) is a corrupt form of normal evolution. =Appearances=

Digimon Adventure
When Taichi aggressively forced Agumon to try to super evolve in "Dark Evolution! Skull Greymon" with disregard to Agumon and the others' feelings Agumon evolved into Skull Greymon. In this form Agumon lost all sense of himself and attacked anything and anyone nearby.

Digimon Adventure 02: Vol. 1: Digimon Hurricane Landing!!/Vol. 2: Transcendent Evolution!! The Golden Digimentals
Lopmon dark evolves to Wendimon.

Digimon Adventure tri.
Meicoomon's evolutions to Meicrackmon: Vicious Mode are through Dark Evolution. In Coexistence, Hikari becomes deeply depressed due to her brother's disappearance. As a form to fully release Meicoomon's destructive power, the Mysterious Man converts Hikari's bad feelings into viral data, forcing Nyaromon to dark evolve into Ofanimon: Falldown Mode, that later fuses with Raguelmon into Ordinemon.

Digimon ReArise
A Tyranomon attacks the town and then dark evolve into a SkullGreymon.

A dark evolution occurs when Yagami Taichi gets swallowed by Done Devimon while Metal Greymon: Alterous Mode watches. The hate and anger felt by the latter pushes him to evolve into Mugendramon.