Heat a large skillet over medium-high heat. Add the ground beef and cook for 4 to 5 minutes, breaking it up as it browns.
Add the diced onion and cook until softened. Stir in the garlic, cumin, chili powder, garlic powder, oregano, salt, and pepper. Cook for about 30 seconds until fragrant.
Transfer the meat mixture to a slow cooker. Add the pinto beans, kidney beans, diced tomatoes with juice, diced tomatoes with green chiles, and tomato sauce.
Stir everything together until well combined. Cover and cook on High for 3 to 4 hours or Low for 6 to 8 hours, until thick and heated through.
Taste and adjust seasoning if needed. Serve hot with optional toppings like shredded cheese, sour cream, or chives.