To be called Machiavellian is to be considered unscrupulous, immoral and deceitful. This is a man that wrote that 'since love and fear can hardly exist together, if we must choose between them, it is far safer to be feared than loved', and 'if an injury has to be done to a man it should be so severe that his vengeance need not be feared'. Machiavelli did not see people as inherently good, but wrote that 'of mankind we may say in general they are fickle, hypocritical, and greedy of gain'.
But in spite of this jaundiced worldview, or maybe because of it, Machiavelli has been called the founder of modern political science and realpolitik, and I believe teaches 5 lessons that can benefit the strategist.