I’ve been lucky enough not to have anything eat my Basil. I did plant it next to Dill, and Parsley so maybe they help keep pests away.

I feel your pain we have same issue

You can try cayenne pepper powder and water.. 3 tablespoons per cup in a spray bottle and spray it on the basil. Don’t need to use much.

Simple dishwashing liquid (about a tablespoon) with water in a spray bottle and spray it. You can also add chilli powder to the mix for good measure just remember to give it all a good wash before using

Companion plant basil with marigolds, is a good move as the team works together to keep pests away. Growing tomatoes and basil near each other is said to make each crop taste better. I have sprinkled/dusted Chilli powder around my basil bugs hate this just wash freshly picked basil well.
You could buy a Insect Cage Garden Portable Incubator Butterfly Habitat Zipper Opening Foldable these work well keeping bugs and butterflies eating your plants.

I head to Bunnings for garden bug spray. It always works

Plant some lemon grass nearby to deter pests or plant basil near citrus trees this will also deter bugs.

I often make a soapy spray with which I treat the leaves.
You might find this article helpful https://homeguides.sfgate.com/can-spray-plants-keep-bugs-away-basil-leaves-90744.html