There are a ton of incredibly deadly animatronics in the FNAF series, and everyone will have certain animatronics that they struggle to beat depending on their playstyle. However, I’d say that Springtrap is among the deadliest since he plays mind games with you, attempting to hide from your cameras and tricking you with hallucinations. FNAF 3 really made things personal, especially in comparison to the first two games. It’s just you and Springtrap trying to outsmart each other while alone in that office together for five long nights, and the game really makes you feel that with Springtrap’s mechanics and AI. Aside from Springtrap, I’d list the Puppet from FNAF 2 as one of the deadliest animatronics since his music box requires constant attention, and there’s nothing you can do to stop him once he’s out of the box. Both Nightmare Fredbear and Nightmare from FNAF 4 are incredibly challenging as well, so much so that they’re both harder to beat on their own than the rest of the game’s animatronics combined.