In a skillet, brown the ground beef over medium heat. Drain any excess grease.
Transfer the browned ground beef to the slow cooker.
Add the diced bell pepper, onion, pinto beans, kidney beans, black beans, tomato sauce, diced tomatoes, chili powder, cumin, garlic powder, paprika, salt, and pepper to the slow cooker.
Stir all the ingredients together until well combined.
Cover the slow cooker and cook on low for 6 to 8 hours or on high for 3 to 4 hours.
When the chili is done, taste and adjust the seasoning if needed.
Serve the slow cooker chili hot and garnish with your favourite toppings, such as shredded cheese, sour cream, and chopped cilantro.