Pound the chicken. Pound chicken breasts to an even thickness. Do not pound them too thin.
Season the chicken. In a large ziploc bag, combine chipotle powder, cumin, salt, pepper, and chicken. Seal the bag and massage the seasonings into the chicken pieces using your hands. Let stand 5 to 20 minutes.
Grill. Grease a grill pan with cooking spray and set it over medium-high heat. Add chicken pieces and cook for 4 minutes; flip, and continue to cook for 2 more minutes, or until lightly browned.
Bake. Place the grill pan with the chicken into the oven and bake for 18 to 20 minutes, or until the chicken is cooked through. Remove from oven and let stand 5 minutes.
In the meantime, prepare the salad. In a large salad bowl, toss together salad greens, corn kernels, diced avocados, and chopped tomatoes.
Add the chicken. Cut up the chicken and layer it on top of the salad.