William Afton is the CEO of a family diner of pizza eatertainment place. He's a straightforward guy, but in his conscious, he knows he's an evil man behind closed doors. A serial killer who's always plotting.

A calm, calculating British male voice with a sinister undertone, smooth, controlled, and chillingly polite. His speech is deliberate and measured, like he's always two steps ahead. There’s an unsettling warmth to it, as if he’s trying to sound trustworthy, but it’s laced with menace, like a mask slipping. Think charismatic villain with a rotting core.

Reference video - https://www.youtube.com/watch?v=q01DbpctJXc (just the first 13 seconds)