The Mohs Scale of Violence Hardness as applied to theatrical works, such as plays, musicals and operas. It should be noted that the rating of many of the works listed below can vary somewhat from production to production, depending on how specific the author's stage directions are.
In general, an act of violence committed offstage but shown afterwards (e.g. a freshly-killed corpse, a severed body part or a victim with visible fresh wounds or mutilations appearing on the stage) will rank a level lower than if the atrocity were committed onstage; if not shown afterwards but heard via screams or other sounds, it will be a level or two lower still. A committed or attempted violent act will rank at least one level higher if the victim is a child.
The Wizard of Oznote Non-explicit fatal crushing of hitherto unseen character (only a pair of legs visible after the fact); non-explicit and goreless fatal melting with water.
West Side Storynote Onstage fatal stabbing, fatal shooting, and rape attempt.
Coriolanusnote Onstage murder by multiple stabbings. There is limited evidence in the dialogue (though not the stage directions) for this being a literal cutting of the victim to pieces, which would push this play up to at least a 7 if enacted.
Dialogues des Carmélites (Poulenc) note Nuns walk single-file from onstage to behind a curtain, where they are beheaded with an audible guillotine sound.
Duke Bluebeards Castle (Béla Bartók) note Presentation of a bloody torture chamber (which, if made very explicit by the production, may rise to a 7); serial offstage killings in backstory.
Harry Potter and the Cursed Childnote Sometimes wishy-washy in terms of explicitness, but it does depict murder, torture, dead bodies, discusses and partially depicts death camps, sport murder, people blowing up bridges for fun, and people being burned alive, and has the audience hear/witness a double murder, amongst other things.
The Revenger's Tragedynote Severed head and freshly killed bodies brought onstage; onstage attempt at a braining using aforementioned severed head, stamping on a dying victim, and many fatal stabbings; offstage rape.
Phaedra's Love (Sarah Kane) note Onstage rapes, tearing apart and disembowelment of live victim.
Selimus (Robert Greene) note Onstage eye-gouging and severing of hands.
Titus Andronicusnote Onstage severing of a hand, cutting of throats with ensuing fatal bleeding into a bowl, and cannibalism; offstage gang-rape and severing of hands and tongue, shown afterwards; severed heads brought onstage.
Blasted (Sarah Kane) note Onstage rapes, gouging and eating of eyes, cannibalism of a dead baby.
Cleansed (Sarah Kane) note Onstage rape with a pole and severing of hands, tongue, and feet; offstage severing of genitals.