Heat a large skillet over medium heat and add the ground turkey. Cook until no longer pink, breaking it up with a spoon as it browns.
Add the diced onion and minced garlic to the skillet. Cook for 3 minutes until the onion softens.
Transfer the turkey mixture to the slow cooker. Add the sweet potato cubes, black beans, kidney beans, diced tomatoes, chicken broth, chili powder, cumin, salt, and black pepper.
Stir everything together until the spices are evenly distributed.
Cover and cook on low for 6 to 7 hours until the sweet potatoes are tender.
Ladle into bowls and top each serving with shredded cheddar cheese and chopped cilantro.