Preheat oven to 425°F (218°C) and line a large baking sheet with parchment paper.
Toss cubed potatoes with olive oil, 1/2 teaspoon of chili powder, 1/2 teaspoon of cumin, and 1/2 teaspoon of garlic powder in a large bowl.
Spread potatoes in a single layer on the baking sheet and roast for 25-30 minutes, turning once, until crispy and golden.
While potatoes roast, heat a large skillet over medium-high heat and brown the ground beef with the diced onions until the meat is no longer pink.
Drain excess grease from the skillet and stir in the remaining chili powder, cumin, garlic powder, and water; simmer for 5 minutes until the sauce thickens.
Warm the black beans and corn in a separate saucepan over medium heat.
Divide the roasted potatoes among four bowls.
Layer the seasoned beef, black beans, and corn over the potatoes.
Garnish each bowl with shredded lettuce, diced tomatoes, cheese, a dollop of sour cream, and fresh cilantro.