Preheat the oven to 450 degrees F.
Toss the shrimp together with the chile powder, 1/2 teaspoon salt, and 2 tablespoons olive oil. Arrange in an even layer on a foil-lined baking sheet. Bake in the oven for 10 minutes, until the shrimp are pink and curled. Set aside.
Bring a large pot of water to boil. Tie the asparagus in a bundle with kitchen twine. Blanche the asparagus for a few minutes, until just tender. Remove with tongs to an ice bath or a colander under cold running water.
Cut the asparagus into 1 inch pieces. Add the pieces from the bottom third of the stalks to a small food processor (about 1 cup). Pulse the asparagus along with 1 cup tightly packed cleaned radish leaves, mint, garlic, lemon juice, ¼ cup of the pepitas, and 1/4 cup olive oil.
Scrub the radishes clean and quarter them lengthwise. Toss together with the vinegar, sugar, and 1/2 teaspoon salt in a small mixing bowl. Toss every 10 minutes or so.
Serve the tacos family style: warmed corn tortillas alongside the shrimp, asparagus pesto, pickled radishes, and chopped asparagus. Garnish with queso fresco and hot sauce, if using.