to say the least
US /tə seɪ ðə liːst/
UK /tə seɪ ðə liːst/

1.
控えめに言っても, 少なくとも
used to indicate that one is understating something, or that the reality is more extreme or significant than what is being explicitly stated
:
•
The meeting was chaotic, to say the least.
会議は混沌としていた、控えめに言っても。
•
His performance was disappointing, to say the least.
彼のパフォーマンスは期待外れだった、控えめに言っても。