stubbornest

adj.顽固的；倔强的；难对付的

That stubborn man always cleaves to his idea. 那固执的人不愿改变想法。

This detergent can remove stubborn stains. 这种去污剂能去除难洗的污渍。

I have a stubborn cold and cough day and night. 我得了很难治的感冒，日夜咳嗽。

You'll have to push hard; that door is a bit stubborn. 你得使劲推，那扇门有点难开。