Char the corn: Heat a dry cast iron skillet or grill pan over high heat. Add 2 cups corn kernels, fresh (about 2 ears) or two cobs without moving for 2–5 minutes until charred in spots. Toss and char another 2–3 minutes. Remove from heat and let cool completely.
Prep the beans: Add 1 Great Northern beans, drained and rinsed (15 oz can) to a large bowl.
Make the dressing: In a small bowl, whisk together 1 lime, juiced, olive oil, garlic, ground cumin, salt, and black pepper until well combined.
Combine: Add the cooled charred corn, pickled banana peppers, diced, red onion, fresh cilantro, chopped to the beans. Pour the dressing over and gently toss to coat everything evenly.
Fold in avocado: Just before serving, gently fold in 2 ripe avocados, diced and banana pepper brine, keeping the avocado chunks intact. Top with cotija cheese, crumbled (topping). Taste and adjust salt only after the cotija is added, as it is quite salty.
Rest and serve: Let sit for 10 minutes at room temperature for flavors to meld. Serve with tortilla chips, pita chips, or sturdy crackers.