To a large pot, add red onion, minced garlic, celery, carrots, potato, tomatoes, chicken bouillon, and chicken breasts.
Add Adobo seasoning, garlic powder, Italian seasoning & pepper, then add water.
Bring pot to a boil on high heat, then cover and reduce heat to medium low. Cook 10-20 minutes, just until veggies have softened and chicken is cooked through.
Transfer the cooked chicken from pot to a plate and set aside. Add broken spaghetti noodles to the pot and cook (covered) for another 10-15 minutes, stirring occasionally, until pasta has cooked to desired tenderness.
While noodles cook, use two forks to shred chicken. Return chicken to the pot once spaghetti is done. Stir well and serve soup warm. Top individual servings with a sprinkle of dried parsley flakes (optional).