In a medium bowl, mix together chili powder, cayenne pepper, garlic powder, cumin, salt, and pepper. Toss the large shrimp in this flavorful mixture until evenly coated.

Heat a tablespoon of olive oil in a large skillet over medium-high heat until it shimmers. Add the shrimp in a single layer and cook for about 2-3 minutes on each side until pink and opaque.

While the shrimp are cooling, combine ripe avocados, sour cream or Mexican crema, fresh cilantro, lime juice, minced garlic, and a pinch of salt in a blender. Blend until smooth and creamy.

Warm the corn or flour tortillas on a skillet until soft and pliable. Fill each tortilla with the cooked shrimp and drizzle avocado crema on top.

Present the tacos on a platter, garnishing with lime wedges and squeeze fresh lime juice over each taco before serving.