In a medium bowl, toss the peeled and deveined shrimp with olive oil, chili powder, sea salt, and black pepper until thoroughly coated.
Preheat a grill or cast-iron grill pan over medium-high heat and cook the shrimp for 2-3 minutes per side until they are pink, opaque, and slightly charred.
While the shrimp cooks, combine the shredded green cabbage, thinly sliced red onion, and chopped cilantro in a large mixing bowl.
In a small bowl or blender, mash the avocado with lime juice and minced garlic, adding a teaspoon of water if needed to reach a creamy dressing consistency.
Pour the avocado dressing over the cabbage mixture and toss well to ensure every ribbon of cabbage is coated.
Divide the crunchy slaw into bowls and top with the warm grilled chili-lime shrimp.