Examples: A soft-spoken person can be a foil to an angry person. A wise person can be the foil to a foolish person. A logical person can be a foil to an illogical person. A kind person can be a foil to a hateful person. A generous person can be a foil to a selfish person. An objective thinker can be a foil to a person who relies upon subjectivisms such as personal opinions. An Ethical Journalism can be the foil to an Unethical Journalism. A reasonable attitude can be the foil to a an outrageous attitude. Pity can be the foil to cruelty. Elaboration can be the foil to brevity. Warmth can be the foil to a chill.

This link explains what a "foil" is, in the context of your question: http://en.wikipedia.org/wiki/Foil_(literature)