Who is the antagonist in "the strangers that came to town? "

In The Strangers That Came to Town, the antagonists would have to be Tom and Andy.  Taking into account the definition of 'antagonist' which speaks to being hostile and actively opposes to someone or something, the boys would best fit the profile.  They were unwilling to get to know the Duvitch family and merely judged them based on their appearance.  Even though the boys' father made an effort to speak to the family the boys showed no regards for them and even went as far as throwing soap into the tub in which the Duvitvch family kept fishes, and this resulted in the sixty-one of the fish dying.

Use who. if it wasn't a question, you could put the he in the blank.  if you can put he or she in the blank, it's who.if you can put him or her in the blank, it's whom.