I think there's a real argument to be made that the Punic Wars had this effect on Rome. Not only did huge numbers of people die, the standing aristocracy was incredibly thinned, opening the way for many new families and otherwise hopeless men who had a chance to both shine, as well as raise their family to unimaginable heights, likely reinvigorating the leadership of the Republic at a critical juncture. Rome also came out of the wars as the undisputed master of the Western Mediterranean.