Place the chicken breast between two pieces of parchment paper and pound to an even thickness of about half an inch.
In a shallow bowl, whisk together the buttermilk and hot sauce, then submerge the chicken and marinate in the refrigerator for at least 30 minutes.
In a separate shallow dish, combine the whole wheat flour, garlic powder, onion powder, paprika, sea salt, and black pepper.
Remove the chicken from the buttermilk, letting excess liquid drip off, then dredge thoroughly in the flour mixture until fully and evenly coated.
Lightly coat the chicken on both sides with avocado oil spray and place in the air fryer basket at 375°F for 12-15 minutes, flipping halfway through until golden.
While the chicken cooks, whisk the Greek yogurt and Dijon mustard in a small bowl to create a protein-packed sandwich spread.
Toast the whole wheat bun until warm, spread the yogurt mixture on the bottom half, then layer with the lettuce, crispy chicken, and pickles.