Combine beans, onion, chili peppers, corn, tomato sauce, diced tomato, cumin, chili powder and taco seasoning in a slow cooker and mix well. Nestle the chicken in to completely cover. Cook on LOW for 8 to 10 hours or on HIGH for 4 to 6 hours. Half hour before serving, remove chicken and shred. Return chicken to slow cooker and stir in.