In a skillet over medium heat, cook the ground beef with the diced onion until the beef is browned and the onions are soft. Add the minced garlic and cook for an additional minute until fragrant. Drain any excess fat.

Transfer the beef mixture to a crockpot. Add the diced tomatoes, tomato sauce, kidney beans, black beans, chili powder, cumin, paprika, cayenne pepper, salt, and pepper. Stir to combine all the ingredients thoroughly. If you prefer a slightly thinner chili, add 1/2 cup of beef broth or water.

Cover and cook on low for 6-8 hours, or on high for 3-4 hours. This slow cooking process allows the flavors to meld together and the chili to become rich and thick.

Once the chili is done, give it a good stir and taste for seasoning. Adjust with more salt, pepper, or spices if needed.

Serve hot in bowls with your choice of toppings such as shredded cheese, sour cream, chopped green onions, cilantro, or diced avocado.