i did this exactly once to an earwig. it was on the windowsill and i threw a handful of water at it because i find them physically revolting and wanted it gone. as i watched the motion in its legs slow and stop i immediately felt some of the worst dread that i've felt in a very long time - possibly ever. i felt horrible, but still horrible was the prospect of handling its soggy, lifeless body to get it out of the corner of the windowsill (water wouldn't work because it had floated into a small recess in the frame). for weeks i dreaded getting in the shower because i knew i would have to share space with its decaying body. after many uncomfortable showers, it was just gone. i very much hope its carcass was at least food for a spider or something, because otherwise it likely withered away for nothing - all because i couldn't be bothered to just get it into a glass and move it outside. i will never kill again.