Springtrap

Springtrap (aka William Afton) was the main antagonist of the Shadow Freddy Saga until Metallix and Blackrabbit's attempts to change fate. Afterwards, he became a support character.

Human
Not much is known about William's look as a human, except that he is tall, slender and was always wearing purple, which gave him the alias of "Purple Man" among people who didn't knew him.

As Springtrap
Springtrap has greenish gold fur and gold eyes. He has buttons on his torso and a ripped right ear. He had a whole bunch of holes in his suit in Fazbear's Fright, which got bigger after the fire at Fazbear's Fright, but those holes got patched.

Human
William's personality is mostly known during his decay into madness. He is known to have a genius level intellect. Although he gains no pleasure in hurting people, he is willing to do anything for his research. However, he also genuinely cares about his family. He is willing to sacrifice his blood reserves for his brother and, after his children and wife died, becoming animatronics, he tries everything in his power to be with them again.

As Springtrap
Under Shadow Freddy's control, Springtrap is cruel and cold-blooded.

After Metallix freed Springtrap from Shadow Freddy's control, he became more light-hearted. He seems remorseful, because of the crimes he caused. He tries his best to repair the mess caused by Gerald Robotnik's deal with the Black Arms, mess he made worse with his murders. He is still loyal to his family, to the point of calling Simon a "bitch-ass motherf*ker" when Ballora is under Shadow Freddy's control, despite the fact Simon is practically a robotic version of William's corpse. As such, his only problem seems to be his insanity caused by his children's and wife's death.