What the Hell, Hero?/Theatre

In Shakespeare's Titus Andronicus, the title character kills his youngest son, Mutius, in the first scene for very little reason and with amazingly little fanfare -- no dying speech, no nothing. He is called out by his remaining sons.
Similarly, in Hamlet, when Hamlet switches a letter ordering his own execution with one ordering the deaths of its bearers (who happen to be his erstwhile schoolmates Rosencrantz and Guildenstern), his friend Horatio calls him on it. Hamlet, however, brushes it off with a glib, "They are not near my conscience," which Horatio seems to accept.
At the climax of Shakespeare's The Tempest, Prospero is actually talked out of his revenge plot when his servant Ariel describes the distress of his captured enemies. Prospero realizes that if Ariel, a spirit of the air, can feel pity for these men, then he as their fellow human being should be compassionate as well.
Wagner's Parsifal actually introduces its eponymous hero this way, with him being reprimanded for senselessly killing a swan. Of course, he's The Fool and has a lot to learn -- he doesn't even know his name at this point.
Fairy tale conglomeration/parody Into the Woods is made of this trope. The entire first act highlights the amorality of various fairy tale favorites in their quests to find 'happily ever after', with a character occasionally calling another out on it. It all comes to a head in the second act, which is dedicated entirely to the various characters dealing with the ramifications of their cutthroat methods. The song 'Your Fault' is a half example of this, tempered from a true 'what the hell' by the fact that the characters are simply scrambling to keep the blame off themselves, which ends in the unanimous decision to blame the Witch. Her response is of course a verbal spanking of epic proportions in 'The Last Midnight' for, aside from their amorality to begin with, wasting time finding blame when they should instead be dealing with the damn problem.
- Though the audience may find themselves thinking the Witch has very little room to talk, what with her abuse of her adopted daughter Rapunzel (even if it's ironically rooted in love), which comes up as way worse than, at least, Cinderella wanting to escape her unhappy home life. (Cinderella's only amoral action, in fact, is participating in blaming the Witch with the others.)

Back to What the Hell, Hero?