In a large bowl, combine the chicken breasts with olive oil, 2 tablespoons of lime juice, chili powder, 1 teaspoon of salt, and black pepper. Toss to coat evenly and let sit for 15 minutes.
Preheat the grill to medium-high heat. Place the marinated breasts on the grill and cook for 6 to 8 minutes per side, or until the internal temperature reaches 165 degrees Fahrenheit. Remove from heat and let rest for 5 minutes.
While the meat rests, prepare the salsa. In a medium bowl, gently mix the corn kernels, halved cherry tomatoes, diced avocado, finely diced red onion, and chopped fresh cilantro.
Drizzle the remaining 1 tablespoon of lime juice and sprinkle the remaining 0.5 teaspoon of salt over the salsa mixture. Toss gently to combine.
Top the rested grilled breasts generously with the fresh avocado corn salsa and serve immediately.