In a large mixing bowl, combine Greek yogurt, shredded cucumber, lemon juice, dill, garlic powder, and a pinch of salt and pepper. Mix thoroughly until smooth.

Fold in shredded chicken, red onion, Kalamata olives (if using), and feta cheese into the tzatziki mixture. Stir gently until coated.

Taste and adjust seasoning with more lemon juice, salt, or pepper as needed.

Cover the bowl with plastic wrap and refrigerate for at least 30 minutes to meld flavors.

Serve chilled, garnished with extra feta, dill, or olive oil.