bête noire 
(bĕt nwär)
(bĕt nwär)n.
One that is particularly disliked or that is to be avoided: "Fidel Castro, the bête noire of American presidents" (Benjamin I. Page).
[French : bête, beast + noire, black.]
- under someone's nose
- under (someone's) thumb
- under someone's thumb
- underspin
- understaff
- understand
- understandability
- understandable
- understandably
- understanding
- understandingly
- understate
- understated
- understatedly
- understatement
- understeer
- understood
- understory
- understratum
- understudy
- undersubscribed
- undersupply
- undersurface
- undertake
- undertaker