但我不得不承认这是事实。翻译成英文

But I can not but confess that this is the truth.

不得不承认的事实：Unmistakable truth
但我不得不承认这是事实：But I must admit it is the truth

fact 指证据却凿，不可动摇的事实。
你那句有回旋余地的应该用 truth

But I have to admit it as a fact.

But I have to conceded that it was the truth.

But I have to admit it is the fact.

But I have to admit this is the fact
have to 不得不 事实 fact