Two facts settle the whole packing question. First, your destination's socket type and voltage, findable in seconds on any standard plug chart or the destination's tourism site: the world runs either roughly 110 to 127 volts or 220 to 240, with over a dozen socket shapes from the flat North American pins to British three-pin and European rounds.
The items that genuinely need thought are single-voltage appliances, almost always heat tools like hair dryers and straighteners, plus some shavers. Options are a proper voltage converter, heavy and mediocre with high-wattage heat tools, a dual-voltage version of the appliance, or simply buying cheap locally, which is what most long-term travelers do since hotels provide dryers anyway.
Pack two adapters rather than one, because they get left in walls, and consider a compact travel power strip with USB ports so one adapter charges everything. Grounded adapters matter for three-pin laptop plugs. Skip airport-priced adapters; buy before you travel or at any local supermarket on arrival.