Bigger Dogs can be a serious threat to Papillons.
Some of the bigger dogs are bred for hunting for instance, and see the Papillons as prey; a rabbit for example.
But also a sweet, laid back larger dog is not a good playmate for Papillons. It can take only their paw landing on their back, while interacting, to break, or injure the Papillons delicate spinal cord.
If you have a bigger dog at home, introduce your Papillon very carefully, with great observation, as far as dominance establishment, feeding time, favored resting spots, toys.
It is best not to leave your Papillon together with a bigger dog alone, when everyone is gone.