foil

1. N-UNCOUNT

Foil consists of sheets of metal as thin as paper. It is used to wrap food in.

3. N-COUNT : usu sing, N for n

If you refer to one thing or person as a foil for another, you approve of the fact that they contrast with each other and go well together, often in a way that makes the second thing or person seem better or less harmful.

• He thought of her serenity as a foil for his intemperance.    
• A cold beer is the perfect foil for a curry.   
• =  complement 

.... Cobuild

foil(2): 

3. One that by contrast underscores or enhances the distinctive characteristics of another: 

• "I am resolved my husband shall not be a rival, but a foil to me" Charlotte Brontë.
  

... Am-Heritage