Cook the pasta: Bring a large pot of salted water to a boil. Add spaghetti and cook according to package instructions (about 8-10 minutes for al dente). Drain, reserving 1/2 cup pasta water, and set aside.
Prepare the shrimp: Pat shrimp dry with paper towels and season with salt, pepper, and smoked paprika. Heat olive oil in a large skillet over medium heat. Add shrimp and cook for 2-3 minutes per side until pink and opaque. Remove and set aside.
Sauté the garlic: In the same skillet, add minced garlic and sauté for 30 seconds until fragrant.
Make the bang bang sauce: In a bowl, whisk together mayonnaise, sweet chili sauce, sriracha, lime juice, and heavy cream. Pour the sauce into the skillet with the garlic and stir over low heat for 1-2 minutes to warm through.
Combine everything: Add cooked pasta and shrimp to the skillet. Toss gently to coat in the sauce. If too thick, add reserved pasta water, 1 tablespoon at a time, until desired consistency is reached.
Garnish and serve: Sprinkle with green onions and optional red pepper flakes. Serve immediately.