If you're playing Vanquish on a powerful computer and enjoying the increased frame rate modern PCs are capable of, you're also playing a much harder game than you need to be thanks to a bug linking your framerate to the amount of damage you take. A fix, however, is imminent.
Video games are weird
When Vanquish released back in 2010, it was a consoles-only affair like most Platinum-developed games have been. Like Bayonetta, though, the game is seeing new life thanks to an apparently otherwise-solid PC release by Sega. On the Xbox 360 and PlayStation 3, Vanquish was limited to 30 frames per second (and sometimes a bit less) by the hardware. This bug comes out of that, and is one of those weird little peeks behind the video-game curtain we get once in a while thanks to weird glitches and bugs.
On those systems, Platinum knew that anything that happened in Vanquish would happen, at the very most, 30 times every second. Tracking anything from controller input to the movement of bullets and enemies to the calculation of damage can be linked to the frame rate to save a few processor cycles here and there on limited hardware.
A consequence of that is that when the game is ported to hardware that can handle higher frame rates, those calculations are happening two, three, or even four times as much. This isn't the first time we've seen a bug like this. Dark Souls 2 hit PC at the same time as its console brethren, but a bug linking frame rates and weapon durability was missed during quality assurance. In short, your weapon took damage every frame it spent in an enemy or wall, so a doubled frame rate meant doubled damage to your weapons.
Video game glitches are weird, and can have strange effects on the games they're in aside from just breaking them. This one is pretty straightforward, but if you want to see some weirder ones, just follow TheStrangeLog on Twitter.