He's unique.

As a native English speaker I have to say that "Take it easy, is one of a kind" makes no sense to me. However "He's one of a kind" means that he is individual, you will not find another like him. Usually used in a positive way.

"Take it easy, it's one of a kind" - maybe you were carrying an object and you were running, and someone said this to you. It means "calm down / be careful, this object is unique / you won't find another one like it". "One of a kind" basically means that the object is unique, there isn't another one anywhere in the world. However we don't always mean it literally - there may be others, but they are hard to find.

'He's one of a kind' = 他很特别 / 唯一的 Take it easy, is one of a kind 我看不懂， 写错了吧？