Muzan Kibutsuji (Demon Slayer)

Once regular humans turn into legendary demon lords with very similar appearance, cunning and cold-blooded, with the ability to possess the body of others and create armies of lesser demons to fulfill their goals, which is achieving true immortality. When they were humans, they had a condition that left them physically handicapped (Muzan suffering from an illness and Onigumo/Naraku being heavily burned), both tend to manipulate people to their side with false promises and hopes before disposing of them when they're no longer needed, both are personally responsible for the events that caused the sword-wielding protagonist to take action against them, and despite their power, both are actually huge cowards, rarely getting involved in direct conflict and are extremely paranoid over the idea that they're not as invincible as they seem, which results in a pitiful breakdown when they're finally defeated. which results in a pitiful breakdown when they're finally defeated.which results in a pitiful breakdown when they're finally defeated, which results in a pitiful breakdown when they're finally defeated.