to put it mildly
成語所屬單字mildly
to put it mildly — 慣用語
1. used to indicate that what you are saying is an understatement — the actual situ
1.慣用語
釋義
說得客氣點；委婉地說
used to indicate that what you are saying is an understatement — the actual situation is much more extreme, serious, or intense than your words suggest.
例句
The restaurant was not very clean, to put it mildly.
The team's performance was disappointing, to put it mildly.