Not just Syria - Iran is a much more troublesome and pernicious threat than Syria, which after all, will pretty much keep the fighting contained within its own borders.
Not that such a containment wouldn’t have tremendous collateral damage, there is no way to turn that aside. Syria stands to be as devastated as Lebanon was following the effort to kick out the PLO from 1982 onward. But the expulsion of the PLO only left room for the Hezbollah to move into what had essentially become a vacuum, as the Christian regime that was in charge was too weakened and devastated to effectively continue resistance.
Lebanon today is a rubble heap. Syria promises to become the same.