单词devil的首字母d需要大写吗

不需要大写。

He was a miserable old devil.

他真是个令人厌烦的老家伙。

He's a crafty old devil.

他是个奸诈狡猾的家伙。

The leader seemed the devil incarnate.

那个首领好像是魔鬼的化身。

I miss the old devil， now that he's gone.

老家伙这一走，我还真想他。

She has convinced herself that she is possessed by the devil.

她确信自己被魔鬼附了身。