Whenever we see someone rise to greatness, we’re inspired by the impressive personal power that they wield. But managing such power can be a dual-edged sword as anyone can attest who has witnessed its unleashing in the manifestation of terrible atrocities. The challenges associated with this issue can become apparent in a variety of arenas, too, including everything from the world geopolitical stage to the everyday theater of family relations. That point gets driven home with riveting clarity in the dark new comedy-drama, “August: Osage County.”