Hey, I kinda like this thread.
I'd give it to Tabuu and the Hands here. The Hands are known to cooperate with each other, while it's arguable that Chipper, Rainbow, and Scott wouldn't cooperate very well. Plus Tabuu has experience manipulating Low 2-C beings like Master Hand, so I doubt he'll have too much of a problem dealing with the God tiers of FNAF World.
As for the Smash characters and the animatronics, the former should excel there as well, just by going by how the characters are portrayed in the Smash verse in the SSE, Trophy descriptions, Codec conversations, etc.
-In the SSE, they are constantly shown fighting (And in some cases, one-shotting) giant robots like Duo (Composed of G&W clones, fought Snake, Lucario, Fox, Sheik, Peach, and Falco), Porky (Fought by Ness and Lucas), Pig King Statue (OHKO'd by Ness), Galleom (Fought by Pkmn Trainer, Ike, Marth and Meta Knight, Lucas destroyed his body to escape from the Subspace bomb), etc.
-King Dedede's hammer was stated to be capable of levelling entire buildings when fully charged up in Snake's conversation with Colonel over the Codec.
-Also via codec, Meta Knight was stated to be capable of breaking the sound barrier when swinging his sword. Marth fought evenly with him in the SSE.
-Barbara, an Assist Trophy, attacks with soundwaves, which the fighters can dodge.
There are plenty more of these, I'm sure. I'm still looking up the feats, but I should probably write a blog post about this instead of listing them.