Star Trek‘s phasers have a top setting that will vaporize a human:
That’s not just overkill, that’s an insane level of overkill. It’s like using a TOW anti-tank missile to target an individual.
And this is one of the things that Star Trek got wrong. Not that it’s necessarily impossible for a weapon the size of a keychain to vaporize a human, but that the process of vaporizing the human wouldn’t utterly trash the surroundings. Face it: you’re converting, oh, 180 pounds of water to steam, and converting the calcium in the bones, the metal and plastic in his clothes, tools, weapons, etc. into plasma. And if the target is also holding a phaser, you’re converting that into vapor, which means that its battery (or whatever the power source is) is going to explode.
Phaser-vaporizing someone on board a spaceship is going to be a disaster, because by converting 180 pounds of water into steam, you’re increasing the volume by a factor of around 1,000. Imagine if the room the target was in suddenly found itself loaded with 1,000 more people. The pressure will blow the hull apart. While a blaster will simply poke a hole in the target, maybe burning their clothes.
Star Trek always made the result of someone getting vaporized pretty… well, sterile. Zap, bright light, gone. But it wouldn’t be like that. If you want to know what someone getting phasered at full power would look like, YouTube provides. Behold the phenomenon of the “Arc Flash,” where enough electrical energy can be dumped into a human to convert said human into a steam explosion. Obviously, this might be considered slightly grisly, so gather the kids around (occurs at 1:14; you can adjust settings to .25 speed to watch the guy go from “normal” to “Hey, he’s a glowing blob, just like in Star Trek” to “Where’d he go?” in three frames):
It’s kinda unclear just what the hell happened here, but it sure looks like the guy was converted into mostly a cloud and a bit of a spray. In any event, there’s no missing the fact that something really quite energetic happened to the guy. The captain of the Klingon scout vessel vaporizes one of his crew on the bridge, they’re going to be scrubbing it down for *days,* assuming that the steam and overpressure doesn’t kill everyone else on the bridge.
It turns out that the arc flash did not vaporize the worker:
(Hat tip to Nyrath.)