In a large skillet set over medium heat, heat 3 tablespoons of the oil until shimmering, about 2 minutes. Add the collards, 1/2 teaspoon salt and 1/4 teaspoon pepper, and saute until just al dente, about 15 minutes.
Remove from the skillet and drain, reserving the cooking liquid. Heat the remaining 1 tablespoon oil in the same skillet over medium heat until shimmering, 1 minute. Add the drained collards and the sugar. Stir until the sugar begins to caramelize, about 15 minutes. Add some of the reserved liquid to help melt down the sugar as needed. Toss in the red pepper flakes, fully coating the collards before serving.