A person who is described as "Machiavellian" is someone who believes that "the end justifies the means."
The word, Machiavellian, is taken from the Italian Philosopher Machiavelli famous work The Prince which is a guide to political strategy.
Someone Machiavellian is cunning, sneaky and lacks moral conduct which Machiavelli, points out that "the end justifies the means" behavior especially among politicians. A Machiavellian person manipulates situations or their benefit by the use of human emotions when suited, and dropping them when not.