Freddy in Smash would be... something alright.
I think I'll throw this opinion out.
There are very few characters that in Smash that would greatly annoy me.
FNAF and Minecraft are two of about five that I would beg to Gods to not be playable. No offence to you people who like them and I'll state the reasons from my view.
For the former, I legit find animatronics one of the creepiest things in existence. I've seen them in the US and I just freaked a little or turned my head everytime they moved and had my headphones in.
In the place I saw them I was like "****, I'm gonna get killed by one of the things aren't I? Like if a Goosebumps novel had actual killing!"
FNAF is pretty much that reaction except dial the horror up to 11..
Mii Costume, fine but playable? Nope.
For the latter, I understand the appeal of Minecraft but it is still the artstyle that puts me off.
I could go into more detail but It'll take an essay.