Preheat the grill over medium-high heat.
Rub the shucked corn with olive oil and place onto the grill and cook until nicely charred on all sides, about 5 minutes per side. Allow to cool slightly prior to removing the kernels and transferring to a large bowl.
Add the cherry tomatoes, avocados, black beans and onions to the grilled corn kernels.
Mix together the 2 tablespoons olive oil, agave, cumin, garlic, lime juice, serrano, cayenne, and salt and black pepper to taste in a separate bowl. Whisk together, as you would to make a vinaigrette, and pour over the corn mixture. Mix together gently so everything is coated well, and then fold in the cilantro and scallions.