Given a category and a set of five words, find the word from the set that does not belong (i.e. is the least relevant) with the other words in the category. Words are separated by commas.

Category: employment activity 
Words: sack, inferno, promote, empower, fire
inferno

Category: emotional status 
Words: board, bored, emotional supports, frustrated, fret
board

Category: moral characteristic 
Words: fair, balanced, unprejudiced, pale, alright

pale