Cook spaghetti in salted boiling water until al dente; drain and set aside
Season chicken with salt, pepper, and garlic powder
Heat oil or butter in a large skillet over medium heat
Cook chicken until browned and fully cooked; remove and slice or shred
In the same skillet, sauté onion, garlic, and bell pepper until softened
Add diced tomatoes, tomato sauce, or cream soup, depending on preferred style
Stir in chicken broth and seasonings such as paprika, Italian seasoning, or chili flakes
Add cooked chicken back to the skillet
Mix in the cooked spaghetti until well coated
Stir in cheese if desired and cook until melted
Adjust seasoning with salt and pepper
Serve hot