Add the diced chicken to the skillet and cook until browned, about 5-7 minutes.
Stir in the chili powder, cumin, paprika, garlic powder, onion powder, salt, and black pepper. Cook for another 5 minutes, until the chicken is fully cooked.
Warm the taco shells according to package instructions.
Assemble the tacos by filling each shell with the chicken mixture, then topping with shredded lettuce, diced tomatoes, and shredded cheese.