And New Zealand it's near-extinct endemic birds, thank to mustelids.

The brought-in-for-some-purpose, escape-to-bush, become-feral, become-pest worked also for cats, dogs, horses ... up-to camels. I am not aware of Australian Feral Elephants but it may exist.

It gave Hawaii no less than thirty-four species of insects introduced as attempted biocontrol of an introduced shrub Lantana. Which still grows freely