- In Cymbeline, the previously Laughably Evil Harmless Villain Cloten crosses it when he plans to kill Posthumus and rape Imogen on top of his corpse. A good thing he is killed by Guiderius before he can do so.
- Claudius from Hamlet crossed this line before the beginning of the story by murdering his brother in his sleep.
- In Henry V, we are expected to root for the English over the French, despite the fact that the English have a very flimsy justification for going to war and the play admits this. So to make sure the audience knows the French are nasty customers, Shakespeare has the French soldiers, when they realize they're going to lose, massacre the teenage boys who carry the English army's supplies, one of the highest war crimes possible in those days.
- In Henry VI Part 3, Queen Margaret taunts a captive York about the murder of his young son, and offers him a cloth stained with the son's blood to dry his tears.
- King Lear:
- Edmund crosses it when he sets his own father up to be tortured. Just in case there's any doubt, he then orders Lear and Cordelia to be hanged in prison. Even he ends up regretting this and hastily trying to stop it.
- Cornwall crosses when he brutally blinds Gloucester.
- Goneril and Regan possibly also cross at this point for fully supporting this action, if they haven't already with their treatment of their father. Plus, at this point, Regan stabs a servant in the back while he is duelling with her husband.
- Lady Macbeth crosses the line by manipulating Macbeth into the murder of Duncan, triggering his Start of Darkness.
- Macbeth himself crosses either by setting killers on Banquo and young Fleance, or by having Macduff's wife and children murdered.
- Don John and Borachio of Much Ado About Nothing cross this line by deliberately setting up Hero to be framed for infidelity on the night before her wedding, which would have led to her life and reputation being ruined, her virtue impugned, and her marriage prospects gone forever.
- For many viewers, Claudio can come pretty close to the MEH for publicly and loudly shaming Hero. Although he has been cruelly manipulated by Don John and Borachio into thinking she was sleeping around on the night before the wedding, there is no way he would have been unaware of the consequences of calling her out in public - rather than, for instance, quietly breaking things off with her.
- Angelo of Measure for Measure crosses when he coerces Isabella into sleeping with him under the promise of saving Claudio, then goes back on his word and orders Claudio's execution anyway. Thank goodness this didn't go quite as he planned.
- In Othello, Iago's crossing is the enactment of his plan to ruin Othello, setting off multiple murders in the process.
- Pericles, Prince of Tyre:
- Antiochus, who is engaged in an incestuous relationship with his daughter, falsely offering her hand to any man who can guess the answer to a riddle, then killing all men who try, regardless of whether or not they can do so.
- Dionyza repaying Pericles' generous salvation of her and her husband during a famine by plotting to murder his daughter Marina out of jealousy.
- Richard II crosses by taking Gaunt's land and money away from Bolingbroke, the rightful heir to them, and Richard is explicitly warned that once he does it there's no going back. He doesn't care.
- For those who know what is to come, Bolingbroke crosses by his deposition and humiliation of Richard, due to the fact that this ends up triggering a struggle for the crown that we now know as The Wars Of The Roses.
- In Richard III, the title character's murder of the Little Princes catapults him over the line and causes many of his allies to rebel against him.
- Not only that, but the play itself rebels against him. Before the murder of the princes, Richard is dazzlingly evil and full of vitality. After their murder, he loses his vitality and his way with words. Taken from him just like *that!*.
- Depending on the production, Tybalt from Romeo and Juliet may cross the line by stabbing Mercutio under Romeo's arm. Some adaptations avert this, such as the Zeffirelli version, in which Tybalt is characterized as a jovial troublemaker who duels with Mercutio all in good fun and kills him by mistake, after which he is visibly horrified.
- In Titus Andronicus, Demetrius, Chiron, Tamora and Aaron all cross the MEH with Lavinia's brutal rape and mutilation: the former two carried it out, Aaron masterminded it, and Tamora fully condoned and encouraged it. And what's worse, Demetrius and Chiron taunt her about it afterwards, mockingly daring her to try and tell anyone who abused her so thoroughly.
- In the last scene of Two Gentlemen of Verona, Proteus tries to rape Silvia (before being talked down by Valentine) and his being rather suddenly forgiven by both Valentine and Julia does not ring true for many modern viewers.
Moral Event Horizon / William Shakespeare