Harry is a super mutant who is a former commander in the Master’s Army. After the defeat of that army at the hands of humans, he and his comrades wandered the wastes looking for purpose. Human bigotry, because of the war, made it hard for them to settle down. Eventually, they made their way to Storm City under the leadership of a mutant who is known only as the Leader. Harry disagreed with the brutal leadership of The Leader and their hatred for humans. Harry and his closest friends then deserted the Leader’s army and he is currently trying to convince even more mutants to leave with him. Harry should come across as wise and smart amongst super mutants.
Harry is more eloquent than most mutants. Think of Michael Dorn from Fallout 2:
https://www.youtube.com/watch?v=iZb4ACwMjEc