Place the chicken thighs in the slow cooker. Add the minced chipotle peppers, diced onion, minced garlic, chicken broth, cumin, salt, and pepper.
Cover and cook on low for 6 hours until the chicken is tender and shreds easily with a fork.
Stir in the chopped kale during the last 30 minutes of cooking so it softens but keeps some texture.
Shred the chicken directly in the slow cooker and mix it with the kale and sauce.
Serve the chicken and kale mixture topped with avocado slices and a squeeze of fresh lime juice.