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: personal characteristic 
Words: ethical, tropical, unflappalbe, cool, optimist
tropical

Category: moral characteristic 
Words: fair, well, impartial, alright, stormy
stormy

Category: type of sandwich 
Words: hero, french toast, open-faced, club, group

group