Merciful Heroes which are the opposite of Sadists are really sympathetic or forgiving to others and are reluctant to kill, including villains that have wronged them in the past. This understandably could rebound on them sometimes, as they refuse to accept that there isn't any other option to kill sometimes, though some are willing to resort to killing when absolutely necessary. For obvious reasons, it is rare for merciful heroes to be lethal.

Many of these types of Heroes can count as Pure of Heart so as long as they have their moral agency understanding between the sides of right and wrong.