-de   as in the meaning of  "frightening and threatening "

-DE can be used to form sentences of  frightening and threatening others.

Geleceği varsa, göreceği de var !

If he will come then he will see !

[ If he ever comes he will get his answer or he will get what he deserves]

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Borcunu beş gün içinde ödeme de görelim, bak  neler olacak.

[ I am warning you] If you don´t pay your debt in 5 days, then see what´s gonna happen !

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Ona dokun da gör !

If you ever dare to touch her/him, you will see what´s gonna happen to you !

[I am warning you ,don´t touch her/him ]