Both the Cambion and the Succubus/Incubus have abilities that allow them to charm a humanoid, who must then obey their commands until the charm effect is broken. However, both include clauses that state that if the charmed humanoid is given a suicidal command, they can repeat the saving throw, ending the charmed condition on a success.
From Cambion (MM, pg. 36):
Fiendish Charm. [...] The charmed target obeys the cambion’s spoken commands. If the target suffers any harm from the cambion or another creature or receives a suicidal command from the cambion, the target can repeat the saving throw, ending the effect on itself on a success.
Charm. [...] The charmed target obeys the fiend's verbal or telepathic commands. If the target suffers any harm or receives a suicidal command, it can repeat the saving throw, ending the effect on a success.
If the charmed humanoid succeeds, clearly they will not do the suicidal thing they were told to do (unless they genuinely wanted to, for some reason).
But what about if they fail? Do they still go ahead with the command, or is the command somehow invalidated but the charm effect persists? If a cambion charmed a barbarian and told them to jump off a massively high cliff, and the barbarian failed the repeated saving throw, would they now jump to their death?