Dice the onion into small, uniform 1/2-inch pieces and set aside. In a large skillet over medium-high heat, brown the ground chicken, breaking it apart with a spoon as it cooks, until no pink remains and the meat is lightly golden (about 5-7 minutes). This step develops deeper flavor through browning rather than simply cooking the chicken through. Once cooked, transfer the chicken to a plate and set aside.

In a small bowl, whisk together the cumin, chili powder, salt, cayenne pepper, and garlic powder. I prefer to use freshly ground chili powder when possible since the flavor is noticeably more vibrant than pre-ground versions. This ensures the spices are evenly distributed throughout the chili rather than settling to the bottom of the crockpot.

Transfer the browned chicken from Step 1 to your crockpot. Add the drained and rinsed kidney beans, both cans of diced tomatoes (including the can with green chiles), the diced onion from Step 1, and the spice mixture from Step 2. Stir everything together thoroughly until well combined, ensuring the spices are evenly distributed throughout.

Cover the crockpot and cook on high for 4 hours. The low and slow cooking allows the flavors to meld beautifully and the beans to soften completely. I like to give it a quick stir about halfway through cooking if you're around, though it's not necessary. The chili is ready when it reaches a rich, deep color and the flavors have fully developed.