In a large skillet over medium-high heat, brown the ground beef until fully cooked.

Add the diced onion to the skillet and cook until softened and translucent, then stir in the minced garlic and cook for an additional 30 seconds.

Sprinkle in the cumin, chili powder, garlic powder, oregano, salt, and black pepper, mixing well.

Transfer the seasoned beef mixture into your slow cooker.

Add in the black beans, kidney beans, diced tomatoes with their juice, diced tomatoes with green chilis, and tomato sauce. Stir everything to combine well.

Cover the slow cooker and set it to cook on low for 6 to 8 hours or on high for 3 to 4 hours.

Once cooked, taste the chili and adjust seasoning if needed. Serve hot with your favorite garnishes.