Dual Persona is an ability introduced in Pika-Fanon. Only one Pokémon, Taijuti is known to possess it, and it cannot have another ability.
Dual Persona changes the appearance of Taijutsu, revealing either the left or right eye. When the left eye is revealed, Taijuti becomes bad tempered and spiteful, and it gains high resistance to Dark-type moves. When the right eye is revealed, it becomes good natured and peaceful. This ability also allows it to survive hits from either Dark Judgement or Purification Wave with remaining health as a Pokémon with Sturdy would be able to stand up to a One-Hit KO move.