Slice the sweet onion into 1/2-inch thick rings and separate them carefully.
In a medium bowl, whisk together the flour, sea salt, black pepper, garlic powder, and smoked paprika.
In a separate bowl, beat the egg whites until they are frothy and light.
Gently whisk the cold light beer into the egg whites, then fold in the flour mixture until a smooth batter forms.
Preheat the air fryer to 375°F and lightly grease the basket with avocado oil.
Dip each onion ring into the batter, allowing the excess to drip off, and place them in a single layer in the air fryer basket.
Air fry for 10-12 minutes, flipping halfway through, until the coating is golden brown and crispy.
While the rings cook, blend the Greek yogurt, chipotle peppers, and lime juice in a small food processor until smooth.
Serve the hot onion rings immediately with the chilled chipotle aioli for dipping.