In a medium bowl, combine two-thirds of the sliced scallions with soy sauce, 2 teaspoons lime juice, toasted sesame oil, and chile-garlic sauce.

Add the tuna cubes and stir until well coated.

Cover the bowl with plastic wrap and refrigerate.

In a medium saucepan, heat the vegetable oil to 350°F (177°C) using a deep-fry thermometer.

In one shallow dish, place the flour.

In another, beat the eggs until blended.

In a third dish, add the panko breadcrumbs.

Drizzle the avocado halves with the remaining lime juice and season with salt.

Dredge the avocado wedges in the flour, shaking off excess, then dip in the eggs, and coat with the panko breadcrumbs, pressing gently to ensure the crumbs adhere.

Working in two batches, fry the avocado wedges, turning once, until golden brown, about 2 minutes per batch.

Transfer to a paper towel–lined plate to drain.

Fill the taco shells with the marinated tuna.

Top with the crispy fried avocado, sliced radishes, and the remaining scallions.