他发誓永远不会对妻子不忠。

He swore he would never be ___unfaithful to his wife.

这部电影对小说原著的改编很不忠实，遗漏了许多关键情节。

The film adaptation was ___unfaithful to the original novel, leaving out many key plot points.

他对自己的承诺不忠实，屡次食言。

He proved ___unfaithful to his promises and repeatedly broke them.