0 a situation in which someone forces you to do something, or to pay them money, by saying that they will tell another person something secret -- 脅迫, 恐喝
1 to get money from someone by threatening to tell a secret or to harm them -- ~を脅迫する, 恐喝する
They used the photographs to blackmail her.
We can complete it step by step however long the road is and it can't be completed however short the road is if you don't even mark your footprint.
道路がどれだけ長くても、一歩一歩完了することができますし、足跡をマークしなければ、道路がどんなに短くても完了することはできません。