during the boss fight where there are two hands trying to electrocute you, you will have to dodge a series of attacks, then you have a chance to spell a word. if you make a "good" word, like LIFE, LOVE, or NICE, you will damage the boss. if you can spell a "bad" word, like FEAR or HATE, you will earn this achievement. each time you spell a word the letters will change for the next one, so if you cannot make a bad word using what you have, just attack the boss and try the next letters. you will kill him if you damage him three times though.
details on how to beat the boss:
*** Spoiler - click to reveal ***after you turn on the switch, the hands will slam down and cause electricity to chase you from the left out of the bottom area. jump out on the right side and wait in the middle. the boss will roar and charge up an attack. as soon as the lights on the floor go dark, jump or you will die. afterwards you can spell a word. if you haven't killed him yet, some flaming As will rain down, which you have to dodge. his hand will smash onto the left side, and then both hands will use electricity from the center and chase you back into the bottom area. from here the boss pattern repeats itself.