Place a large skillet over medium heat. Add the olive oil; once hot, add the peppers, onion, ½ teaspoon garlic powder, ½ teaspoon onion powder, salt, and pepper. Stir to combine.
Cook until the vegetables are softened, stirring occasionally, about 5-6 minutes. Take off the heat.
Spray an 8-quart slow cooker with cooking spray. Place the chicken into the bottom of the pot.
Crumble the bouillon and sprinkle it over the chicken. Sprinkle the remaining garlic powder and onion powder on top. Add the adobo and cumin.
Pour the chicken broth around the chicken, then add the peppers and onions.
Place the lid on and cook for 6-8 hours on low or 2-4 hours on high.
Shred the chicken in the pot using two forks or an electric mixer and mix everything together. If using an electric mixer, be careful not to overmix otherwise the chicken will resemble canned tuna fish.
Serve with warm tortillas, limes, and guacamole, if desired.