Preheat a grill or griddle using low to medium heat. While the grill heats, season the chicken. Trim any excess fat off the chicken then sprinkle both sides with salt, garlic powder, onion powder, chili powder, chipotle, and cumin.

Brush the grill/griddle with oil, and lay the chicken breasts onto the hot grill. Cook the chicken for 8 to 10 minutes on each side. An instant read thermometer should read 165° degrees when inserted in the thickest part of the chicken and the juices should run clear. 

After the chicken cooks, remove from the pan, set on a waiting plate, and cover with foil. Allow the chicken to rest for at least 10 minutes before slicing. While the chicken rests, assemble the salad.

Place the lettuce, corn, tomatoes, avocado, and onion in a large bowl. Toss to combine. Slice the chicken into several pieces and lay over the top of the salad. Drizzle with spicy ranch dressing.