Preheat 350°F. Spray a 9X13 inch baking dish with nonstick cooking spray; set aside.
Heat vegetable oil (2 tablespoons) in a large skillet over medium heat. Saute onion (1), stirring frequently, until translucent, about 6 minutes. Add garlic (4 cloves), stirring constantly, and saute until fragrant, about 1 minute. Add beef (1 pound), continue to cook, crumbling with a spoon until there is no longer any pink. Drain excess fat from skillet.
Sprinkle beef with chili powder (2 tablespoons), cumin (1 1/2 teaspoons), oregano (1 teaspoon), salt (1 teaspoon), pepper (1/2 teaspoon), and brown sugar (1/2 teaspoon). Continue to cook, stirring frequently, over medium heat until the spices become fragrant.
Stir in black beans (1 (15-ounce) can), pinto beans (1 (15-ounce) can, diced tomatoes (1 (14.5-ounce) can, green chiles (1 (4-ounce) can, sour cream (1/2 cup), 1 cup of cheddar, and hot sauce (1 teaspoon). Cook until the liquid thickens slightly, about 5 minutes. Mix in frozen corn (1 cup), then pour it into the prepared baking dish.
Arrange a single layer of tater tots (1 (32-ounce) bag) over the beef mixture. Cover the dish tightly with aluminum foil and bake for 30 minutes.
Remove from oven, remove and discard aluminum foil, and sprinkle cheese (1 cup) evenly over tater tots. Return to oven for 20 minutes, or until casserole is bubbly around the edges. Allow to cool slightly then serve.