Season the chicken breasts all over with salt, pepper, and garlic powder.
Preheat your gas grill. Set the flames to medium, add the chicken breasts, and grill, covered, until cooked through (~170 degrees F internally), about 15 minutes, flipping them halfway. Transfer them to a cutting board and slice or chop into bite-size pieces.
In a small bowl, make the vinaigrette. Whisk the cider vinegar, honey, dijon mustard, olive oil, salt, and pepper until combined.
In a large bowl, toss the kale with the apricots, avocado, pistachios, white onion, and the vinaigrette. Divide among 4 plates or bowls and top evenly with grilled chicken.