Add ground beef, ground sausage, and onion to an 8-Quart dutch oven or stockpot. Saute onion and meat until the onion is soft and translucent and the meats are no longer pink. (If you are using lean meats or swapping out the sausage, you can add a tablespoon of olive or canola oil to help with the sauteeing).
Add remaining ingredients: white beans, pinto beans, kidney beans, chili seasoning, diced tomatoes, and tomato paste. Beans do not need to be rinsed or drained. Include the juices from the cans of all ingredients.
Stir and heat over medium until chili comes to a boil. Reduce heat, cover, and simmer for at least 30 minutes, stirring occasionally.
Remove from heat.
Serve with freshly grated cheese, green onions, jalapeno slices, sour cream, chips and/or cornbread!