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: