Heat a large pot or Dutch oven over medium heat. Add the ground beef, chopped onion, and chopped green bell pepper, then cook while breaking the beef into small pieces until the meat is browned and the vegetables begin to soften.

Drain excess fat from the pot if necessary. Leave the browned beef and vegetables in the pot so their savory flavor can blend with the tomato mixture.

Add the undrained diced tomatoes, tomato sauce, drained and rinsed kidney beans, and undrained chili beans. Stir carefully until the ingredients are evenly combined.

Stir in the chili powder, salt, and black pepper. Bring the chili to a gentle boil, watching the pot so it does not scorch on the bottom.

Reduce the heat to low, partially cover the pot, and simmer for 40–60 minutes. Stir occasionally as the chili thickens and the tomatoes, beans, beef, and seasonings develop a fuller flavor.

Taste the finished chili and adjust the salt or chili powder if needed. Spoon it into bowls and serve hot with cheddar cheese, sour cream, crackers, cornbread, or chopped onion.