I learned that the only Korean grammar that can express the meaning "must" : (으)면 안 되다.
But I am not so sure if this can mean an absolute "must" in this case as the meaning for it should be "If..., not OK" and I think it is not strong enough.
Example: 이렇게 하면 안 돼! -> Don't ever do it( or else you will suffer a lot,etc.)
I am actually asking for a Korean equivalent for a Chinese vocabulary. This word can be used in any situation as long as the meaning "must" and the imperative mood is conveyed. If you are interested, it is 千萬(it is not meaning 10 million here, but only a word to intensify imperative negation)
Example where it is used:
A friend recommended an insurance service. However I doubt that the company is actually trustworthy, so I tell him "(You must not)Don't ever trust them (千萬不要相信他們)"
A child wants to play Bungee jump. This child's parents are afraid of the potential dangers of the game, so they said "(You must not)Don't ever play this (千萬不要去)"
I could think of the word 절대(로), such as "절대로 그 놈들을 믿지 마", to express the meaning "You must not do it". But I think it is a bit weird. (It is just a feeling, I am not sure)
Anyone who can tell how I should express the word stated above?