01 - Preheat oven to 375°F. Lightly grease a 9x13 inch baking dish.
02 - In a large bowl, combine shredded chicken, 1 cup enchilada sauce, black beans, corn, red onion, cumin, chili powder, garlic powder, salt, and pepper. Mix until thoroughly incorporated.
03 - Spread 1/2 cup enchilada sauce evenly across the bottom of the prepared baking dish.
04 - Arrange four tortillas over the sauce, tearing as necessary to fit and cover completely.
05 - Distribute half the chicken mixture evenly over the tortillas. Sprinkle with 2/3 cup shredded cheese.
06 - Place another layer of tortillas over the filling. Top with remaining chicken mixture and another 2/3 cup cheese.
07 - Arrange final tortilla layer on top. Pour remaining 1/2 cup enchilada sauce evenly over surface. Top with remaining cheese and olives if desired.
08 - Cover dish with foil. Bake for 20 minutes.
09 - Remove foil and continue baking for 10 minutes until cheese is bubbly and golden brown.
10 - Let casserole rest for 5 minutes. Garnish with cilantro, green onions, and avocado. Serve with sour cream and lime wedges.