Preheat a grill over medium-high heat to about 450 degrees. In a small bowl, whisk together 1 tsp of chili powder, 1 tsp of cumin, 3/4 tsp of salt, 1/4 tsp of pepper, and 1/4 tsp of sugar.
Brush the chicken breasts with 1 Tbsp of olive oil and season both sides with the chili powder mixture.
Grill chicken for about 5 to 6 minutes on each side until thickest part of chicken registers 165 degrees. Let rest on cutting board for 5 minutes, then dice into small cubes.
If using fresh corn, grill shucked corn on medium-high heat, turning every 3 minutes until slightly charred, about 9 minutes total. Cut kernels from cobs.
In a large pot, heat the remaining 1 Tbsp of olive oil over medium heat. Add diced onion and sauté for about 5 minutes until translucent.
Add the diced jalapeños and minced garlic, sautéing for an additional 2 minutes.
Pour in the chicken broth, add the fire-roasted tomatoes, remaining spices, salt, and pepper to taste. Bring to a light boil over medium-high heat.
Once boiling, reduce heat to medium-low, cover, and simmer for 15 minutes. If using frozen corn, add during the last 5 minutes of cooking.
Add the diced chicken and corn to the soup, along with cilantro and lime juice. Stir gently to combine.
Serve hot, garnished with diced avocado, shredded Mexican cheese, sour cream, and tortilla strips.
