Nasrallah has far more enemies than friends in Lebanon, but that doesn't mean he can be defeated. The Israel Defense Force is the toughest and most sophisticated military force in the region, yet its soldiers were not able to crush Hezbollah in the July War of 2006, nor during their occupation of South Lebanon that lasted throughout the 1990's. Hezbollah's Lebanese enemies are the weakest in the region. No one should expect them to fare better than the Israelis.
Still, Hezbollah is a guerrilla army, not an occupation force. Counterinsurgency is not in its toolbox. Hassan Nasrallah will have a rude awakening if he tries to emulate Hamas in Gaza and seize the whole country. "No victor, no vanquished" is the rule Lebanese live by in both politics and war, and every faction that has ever tried to dominate Lebanon has learned it the hard way. Whether Nasrallah has learned this near-iron law from the mistakes of others isn't yet clear, but the stiff resistance his men faced in the Chouf, and the recent ominous threats from radical Sunnis, should give him pause at the least. Fifteen years of civil war (1975 to 1990) proved that no one in Lebanon is strong enough to hold the country together or utterly defeat their enemies.
Nasrallah can bully the Lebanese government and render it effectively obsolete, at least on foreign policy questions, but he cannot conquer and administer the entire country himself. Unless the Syrian military returns in full force, Lebanon's future will not be one of dictatorship. Its future most likely will resemble its past--a grim stalemate of schism and internal war.