Dice the onion, and chop the garlic. Cook the ground beef with the onion and garlic in a large frying pan over medium heat. Usually, I cook it in two batches. Drain thoroughly. Transfer the mixture to the slow cooker.
Add the kidney beans, black beans, corn, green chiles, tomato sauce, and beef broth or water. Mix until combined.
Add the chili powder, cumin, sugar, salt, and pepper. Mix until combined.
Cook on low for 3-4 hours or until the chili is heated through and thickened to your desired consistency.
Let rest for 5 minutes before serving with shredded cheese and sour cream.