In a skillet, heat the olive oil over medium heat. Add the shredded chicken, chili powder, cumin, garlic powder, onion powder, salt, and black pepper. Stir to combine and cook for about 5 minutes, until heated through.
While the chicken is cooking, warm the corn tortillas in a separate skillet over medium heat for about 30 seconds on each side, or until pliable.
To assemble the tacos, place a generous amount of the seasoned chicken on each tortilla.
Top the chicken with diced tomatoes, shredded lettuce, diced red onion, and chopped cilantro.
Squeeze fresh lime juice over the tacos and add sour cream or avocado if desired.
Serve immediately and enjoy!