Is Niccolò Machiavelli's political theory--the ends justify the means--incompatible with the Knights Radiant's First Oath?
Brandon Sanderson (paraphrased)
No. Although many of the Orders of Knights Radiant would find Machiavelli's theory, that the ends justify the means, incompatible with additional oaths and/or values of that Order, there are some Orders who could accept a Machiavellian. (Brandon said that the Skybreakers are where a Machiavellian could find a home.)