Rinse the peeled and deveined shrimp under cold water and pat them dry. In a medium bowl, toss the shrimp with olive oil, minced garlic, chili powder, cumin, salt, and pepper until evenly coated.
Heat a skillet over medium-high heat. Once hot, add the shrimp in a single layer. Cook for about 2 minutes on each side until the shrimp turn pink and opaque. Avoid overcrowding the pan; if needed, cook in batches. Remove shrimp from heat and set aside.
In a mixing bowl, combine shredded green cabbage, diced tomatoes, chopped cilantro, and the juice of one lime. Toss everything together until the cabbage is well coated and the flavors meld. Season with a pinch of salt and pepper to taste.
Heat the corn tortillas in a dry skillet for about 30 seconds on each side or wrap them in a damp paper towel and microwave for 20-30 seconds until warm and pliable.
Layer each tortilla with a handful of slaw, a few garlic shrimp, and top with sliced avocado. Serve immediately for the best taste and texture.