Heat a large skillet over medium-high heat and cook the ground beef for 4 to 5 minutes, breaking it into small crumbles with a spatula. The beef should lose its raw color and release some fat while still looking moist.

Add the diced onion and cook for 4 to 5 minutes, then stir in the minced garlic, cumin powder, chili powder, garlic powder, dried oregano, salt, and black pepper for 30 seconds before moving everything to a 6 Qt slow cooker. The onion should be tender and the spice-coated beef should smell fragrant and look deep red-brown.

Stir in the black beans, kidney beans, diced tomatoes, diced tomatoes and green chilis, and tomato sauce, then cover and cook on high for 3 to 4 hours or low for 6 to 8 hours. The chili is ready when it looks glossy and thick, the beans yield easily against a spoon, and the beef smells deeply savory.