Combine 2 teaspoons sugar, chipotle and ancho powders and salt (to taste) in a shallow dish.
Add shrimp to spice mixture; toss well to coat; set aside.
Heat 1 tablespoon oil in a large nonstick skillet over medium-high heat. Add onion, bell pepper, garlic and ginger to pan; saute 3 minutes.
Add 1 1/2 teaspoons sugar and corn to pan; cook 3 minutes, stirring occasionally. Stir in vinegar; cook 30 seconds. Transfer corn mixture to a bowl; stir in salt and green onions.
Wipe pan with a paper towel. Heat 1 1/2 tablespoon oil in pan over medium-high heat. Add shrimp to pan; saute 3 minutes or until done, turning once. Serve shrimp over corn relish and top with avocado, if desired.