While the rest of the animatronics clearly look like metal versions of adorable and cuddly animals, Springtrap goes a whole different direction. That direction is purely into nightmare fuel territory.
Springtrap looks more like a rotting corpse than a bear or chicken, and according to the lore, may actually house the decomposing remains of child killer William Afton.
More than just looking like something only a madman could come up with, Springtrap is more menacing because he can enter any room as well as travel through the vents in FNAF 3. Coupled with the fact that he actively tries to hide from you, Springtrap is a devious and frightening villain when he appears in the series.