Blend the Marinade: In a blender, combine pineapple juice, white vinegar, lime juice, coarsely chopped onion, garlic, cumin, oregano, cinnamon, achiote paste, and guajillo chili powder. Blend on high speed until smooth.

Marinate the Chicken: Place the chicken thighs in a bowl or resealable bag, pour the marinade over, and refrigerate for at least 2 hours or overnight.

Heat the Skillet: Heat olive oil in a large skillet over medium-high heat until shimmering.

Cook the Chicken: Place marinated chicken in the skillet and cook for about 8-10 minutes on each side until fully cooked.

Sauté the Pineapple: Add pineapple chunks to the skillet and sauté for 2-3 minutes until caramelized.

Rest and Serve: Transfer chicken to a cutting board, let rest, slice, and serve hot garnished with caramelized pineapple.