In a bowl, whisk together the fresh lime juice, minced garlic, olive oil, chili powder, cumin, salt, and pepper. Mix well until all the ingredients are blended and aromatic.

Place the chicken breasts into a resealable bag. Pour the marinade over the chicken, seal the bag tightly, and refrigerate for at least 30 minutes.

Preheat your grill or skillet to medium heat. Remove the chicken from the marinade, letting the excess drip off. Grill each breast for about 6-7 minutes on each side, or until thoroughly cooked.

While the chicken is cooking, slice the ripe avocados in half, remove the pit, and drizzle lime juice over them.

Slice the grilled chicken into portions and arrange it on your plates. Top with avocado slices and freshly chopped cilantro.