Combine chili powder, kosher salt, cumin, garlic powder, paprika, dried cilantro, cayenne, adobo, coriander, and oregano in small bowl.
Clean and trim fat from chicken thighs, pat dry.
Coat both sides of chicken thighs with seasoning mix and allow to marinate overnight (preferably).
Heat olive oil in slow cooker (or pan) on sauté function (high). Flash sear chicken thighs, 30 seconds per side, and set aside.
Pour tomatoes into slow cooker and place seared chicken thighs on top. Add lime juice, onions, and bell peppers; follow this particular order.
Season with kosher salt and cracked black pepper. Slow cook on low for 6-8 hours.
Toward the end of cooking, remove chicken thighs and cut into slices (or shred using forks). Stir in cooked chicken and remove excess juices from slow cooker.
Serve with warm tortillas and your favorite toppings.