Scud
Scud may not be totally antagonistic towards the party, but we already know he just can’t help attacking something small that moves. Sid’s dog serves as one of the main threats in the first Toy Story movie, and to a toy he’s certainly a dangerous creature. It looks like the humans have all but disappeared in the Toy Story world of Kingdom Hearts III, but there’s no reason for Scud to be gone.
As you make your way out of Andy’s house and down the street it’s more than likely you could run into Scud patrolling the neighborhood. This could easily be a different kind of boss you’ll just have to run from or avoid in some way, as he chases you down the street. Considering the sheer size difference, Scud could be something similar to the Ground Shaker boss from Kingdom Hearts II, requiring you to get up on his back. It’d certainly add some interesting variety to the Toy-filled world.