Heat a large skillet over medium-high heat. Cook and stir ground beef in the hot skillet until browned and crumbly, 5 to 7 minutes. Drain and discard grease.
Combine ground beef, kidney beans, diced tomatoes, tomato sauce, onions, bell pepper, garlic, chili powder, cayenne pepper, salt, and black pepper in a slow cooker. Cover and cook on Low for 10 hours or High for 4 hours.
Garnish each serving with Cheddar cheese.
