In a mixing bowl, combine dark chili powder, smoked paprika, ground cumin, dried oregano, minced garlic, red pepper flakes, kosher salt, lime juice, and avocado oil. Add uncooked shrimp, coat thoroughly, cover, and refrigerate for up to 30 minutes.

While the shrimp marinates, add avocado, garlic, jalapeño, cilantro, lime juice, Greek yogurt, and water to a food processor. Blend until smooth, adjusting consistency with more water if needed.

In a medium bowl, mix shredded green and purple cabbage. Add some avocado crema and toss gently to coat.

Heat a cast-iron skillet over medium-high heat. Cook marinated shrimp in a single layer for 4-6 minutes, turning once, until they curl and turn pink.

Warm tortillas in a dry skillet for 30 seconds on each side. Assemble tacos with shrimp, slaw, and extra avocado crema.