防不勝防（防不勝防）　

◎ 防不勝防 fángbùshèngfáng

[impossible to defend effectively;cannot reckon with all eventualities;be not easy to guard against;cannot stand up to] 要防的事太多,提防不過來

這種小人,真是防不勝防。——清· 吳趼人《二十年目睹之怪現(xiàn)狀》