Prepare the spice mix by combining chili powder, cayenne pepper, garlic powder, cumin, salt, and pepper in a small bowl. Stir well and set aside.

Coat the thawed shrimp with the spice mixture in a mixing bowl, ensuring they are evenly covered. Let sit for 5 minutes.

Heat olive oil in a skillet over medium-high heat and cook shrimp in a single layer for 2-3 minutes on each side until opaque and curled.

Make the avocado crema by blending avocados, sour cream, cilantro, lime juice, garlic, and a pinch of salt until smooth. Adjust seasoning if necessary.

Warm tortillas in a dry skillet for about 30 seconds on each side. Assemble tacos by layering cooked shrimp, avocado crema, radish slices, and red onion.

Serve immediately with lime wedges for squeezing over the tacos.