In a medium bowl, combine olive oil, lime juice, and chili powder. Add smoked paprika, cumin, garlic powder, onion powder, oregano, cayenne, salt, and black pepper. Whisk until well blended.

Place chicken thighs in a large resealable bag and pour marinade over chicken. Seal tightly and refrigerate for at least 30 minutes, ideally 2-4 hours or overnight.

In a saucepan, combine vinegar, water, sugar, and a pinch of salt. Bring to a simmer. Pour over sliced red onion in a jar and let cool before refrigerating for at least 30 minutes.

Heat a skillet over medium-high heat. Remove chicken from marinade and cook for 5-7 minutes per side until cooked through.

Warm tortillas in a separate skillet for about 30 seconds on each side.

Let the cooked chicken rest before shredding. Assemble tacos by layering shredded chicken, onions, cilantro, and lime juice on each tortilla. Add salsa and pickled onions.

Serve immediately with lime wedges.