In a large skillet over medium heat, brown the ground beef with the chopped onion, stirring occasionally for about 5-7 minutes until the meat is no longer pink and the onion is translucent.

Transfer the browned beef and onion mixture into a 3-quart slow cooker. Add the diced tomatoes, black beans, pinto beans, chopped green chiles, and corn. Sprinkle in your taco seasoning, stirring until well combined.

Cover the slow cooker and set it to low for 8-9 hours or high for 4-5 hours. Stir occasionally during the last half of the cooking time.

Check the chili's consistency towards the end of cooking. For a thicker chili, let it cook uncovered for the last 30 minutes.

Once complete, stir the chili, taste for seasoning, and serve in bowls, garnishing with toppings like shredded cheese or fresh jalapeños.