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Machiavellian
Negative Connotation
The word 'machiavellian' has negative overtones; using it suggests disapproval of the described tactics or behavior. 
Cultural Reference
Originates from Niccolò Machiavelli, an Italian Renaissance writer whose works imply the ends justify the means. 
Often Political
'Machiavellian' is frequently used in the context of political power plays and strategies. 