to put it mildly
idiomPart ofmildly
to put it mildly — idiom
1. used to indicate that what you are saying is an understatement — the actual situ
1.idiom
Definition
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.
Example
The restaurant was not very clean, to put it mildly.
The team's performance was disappointing, to put it mildly.