“士兵不能心软”用英语怎么说？

A solider shouldn't be merciful.用shouldn't比较好，是应当不应当的意思，can是能不能。士兵能心软也能不心软，关键是应不应当心软。

Soldier can't be merciful
用merciful 仁慈的 好一些

Soldier must not be merciful.

soldier can't have mercy on the enemy.

Soldiers can not be softheartedness.

A soldier can't be softhearted.