I wondered at the beginning whether the thread title should have been "Neighbour's nasty cat", as my suggestion shouldn't be applied to a nasty neighbour.
I have long held the view that any cat outside its owner's property should be regarded as a feral cat. There was a time when I inclined to the view that a sudden and quiet exposure to a very heavy metal was a good way to deal with feral cats; while effective, it caused me to lose out with a wonderful lady who thought all cats that had been dumped in my local Reserve were lovely creatures with a right to be there rather than be summarily dealt with. C'est la vie! Irony intended.
Given that there are laws against such behaviour and the desire to get along with neighbours limits similar actions, I can recommend acquiring a friendly dog with a healthy sense of territoriality that befriends residents but warns nonresidents to look to their loins. Although I prefer macropods and small marsupials around my house (meaning I don't keep either dogs or cats) I've had various friends tell me that dogs can be quite effective in discriminating positively to a resident cat and against nonresident cats.