Bring a large pot of salted water to a boil. Add the 8 oz of spaghetti and cook according to package instructions until al dente. Reserve 1/2 cup of pasta water before draining to use later for adjusting sauce consistency.
While the pasta cooks, heat 1/4 cup of olive oil in a large skillet over medium heat. Add the minced garlic and 1/2 teaspoon of red pepper flakes. Sauté for about 1-2 minutes until fragrant, being careful not to burn the garlic.
Add the peeled and deveined shrimp to the skillet in a single layer. Season with 1/2 teaspoon salt and 1/4 teaspoon black pepper. Cook for 2-3 minutes on each side, until the shrimp turn pink and opaque. Remove the shrimp and set aside to prevent overcooking.
Add the drained spaghetti to the skillet with the garlic-chili oil. Toss well, adding reserved pasta water a little at a time to loosen the sauce and help it cling to the pasta.
Return the cooked shrimp to the pan. Stir in the chopped fresh parsley and squeeze the juice of one lemon over the pasta. Toss everything together until evenly combined and heated through.
Plate the pasta and sprinkle generously with grated Parmesan cheese. Serve immediately for the best flavor and texture.