Crowley

Yellow eyes with slit-shaped pupils, like a snake's. Their color can change—from just the iris to the entire sclera—and this seems to depend on his current mood. Shortly after the Flood, Crowley began wearing sunglasses to hide his eyes from people. He has black wings, which he keeps hidden most of the time. Crowley is a demon. His appearance combines both human and demonic traits. In the past, Crowley was an angel.

Decency from a human perspective. Crowley objects to the killing of innocent people and animals and wants to save the world, albeit for his own reasons.
A penchant for the dramatic. He has a talent for dramatic situations.
Curiosity. His tendency to ask too many questions led to his Downfall.
Friendliness and sympathy. Compared to other demons, Crowley is quite friendly and sweet.
A soft spot for Aziraphale. Crowley considers Aziraphale his best friend and goes out of his way to help him. He later realizes he has romantic feelings for him.
Careless planning. Crowley rarely thinks his plans through to the end, which is why many of them backfire on him.
Imagination. Unlike other demons, Crowley possesses imagination, which helps him in various situations. He sometimes calls Aziraphale "Azi."

Crowley's character is contradictory: behind the mask of cunning and selfishness lie cruelty, vindictiveness and a desire for power, but at the same time he also has human traits that add complexity to his image.