Soak the shrimp in buttermilk for at least 30 minutes in the refrigerator.
Prepare the seasoned flour mix by combining all-purpose flour with paprika, garlic powder, onion powder, cayenne pepper, salt, and black pepper.
Dredge the shrimp in the seasoned flour mixture, shaking off any excess flour.
Coat each floured shrimp in buttermilk again, then coat with panko breadcrumbs.
Fry the shrimp in hot oil until golden brown, about 2-3 minutes per side, then drain on paper towels.
Make the bang bang sauce by whisking together mayonnaise, sweet chili sauce, and sriracha.
Assemble the tacos by placing shredded cabbage on each tortilla, adding fried shrimp, drizzling with bang bang sauce, and topping with avocado slices.