What about Lion King where both Scar and the Hyenas talk?

If your answer is that it was one of the few movies where the presence of humans is absent so all animals talk to give the bad guys character and personality, then what about Jungle Book? Both Kaa and Sheir Khan speak.

I’m not counting either Robin Hood or the Great Mouse Detective because both of those have the easy argument that they are anthropomorphic (even more than usual) animals and replace the people who would’ve had a speaking roll.

Lackeys or side-kicks often can speak as well.

In the Fox and the Hound the older dog Chief is a “bad guy lackey” and he is able to talk. As is Iago the parrot from Aladdin, and the two eels Flotsam and Jetsam from the Little Mermaid both have a line or two.

In the end I think it’s less about the type of animal and more about the personality/charactization of the animal. If it’s supposed to be vicious and kill a baby (ie Tarzan) then there’s no real voice or dialog you can add in a kids movie to make it more terrible.