Boil chicken, reserving broth. In large saucepan or medium stockpot, combine tomato soup and equal amount of reserved broth. Add milk, butter, sugar and onion. Bring to a boil while deboning chicken. Once broth is at a full rolling boil, add corn, Rotel tomatoes and chicken. Season to taste. Bring to rolling boil again and add spaghetti. Once noodles are done, it is ready.