WordNet sense 1 (playful in an appealingly bold way):

devilish, roguish

WordNet sense 2 (full of fun and high spirits):

playful

WordNet sense 3 (lacking principles or scruples):

scoundrelly, blackguardly

WordNet sense 4 (deceptive or fraudulent; disposed to cheat or defraud or deceive):

dishonest, dishonorable