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None.
There are a number of scenes of space combat between the Enterprise and Reliant. During interior "explosion" scenes, crewmen can be seen to be killed in the blasts. In a scene set in sickbay, a number of characters die, including one shown to be horribly charred and bloodied, who speaks for a brief moment with Kirk before dying. Khan is terribly burned near the end of the film by an explosion. Spock is shown with lesions oozing green blood as he dies from radiation poisoning. Bloody corpses are hung from rafters on Regula One by Khan's men. Two characters are disintigrated by phaser fire. Depending on the cut of the film, the exit of the Ceti Eel from Chekov's ear can be bloody (some cuts had a extreme closeup of a model of Walter Koenig's ear, with blood oozing out as the eel model exited).
Mild profanity, e.g. "damn" or "hell."
Two characters consume a fictional alcoholic beverage which is illegal (and implied to be very potent from the character's reaction to it).
A character runs into a bloody corpse hanging from the ceiling. Two characters shown scarred and/or crippled from battle. A character is very visibly deteriorated from radiation poisoning and dies slowly. Two characters have small parasitic creatures put in their ears and scream in agony. A scene where a character shoots and disintegrates himself with a weapon may also be unsettling to small children.
