In a large Ziploc bag, combine the buffalo sauce, butter, vinegar, and garlic powder. Close the bag and shake until all the ingredients get incorporated.
Add the chicken legs into a Ziploc bag and place in the refrigerator for 1 hour to marinate.
Place the chicken legs into the basket of the air fryer, save the remaining marinade for later. Set the air fryer to 400° for 25 minutes. Flip the chicken halfway through the cooking time.
If you wish to brush the chicken with the remaining marinade, simply transfer it to a pot over medium-high heat and boil until the marinade is reduced (thickened).