Diabolical

1. (Adjective) - Dubious, scandalous, or otherwise brilliantly devilish; descriptive of behavior conducive to an atmosphere of mischief - generally said of lollygaggers, tomfoolerers, jokers, hoaxers, tricksters, jokesmiths, humorists, jesters, hooligans, goofballs, charlatans, scoundrels, rapscallions, miscreants, jokesters, japers, hoodlums, scallywags, clowns, quipsters, harlequins, buffoons, wisecrackers, rascals, neerdowells, rabbel-rousers, shenaniganizers, goofsters, merrymakers, ruffians, skylarkers, goobers, knuckleheads, and other ridiculous men.

Matt: "Eyy big slime, them fools over in room 306 done pulled a prank on our room!"
Big Slime: "We finna get them back. You know what will really teach them a lesson? We should sneak into their room and pour water in the sinks!"
Matt: "Diabolical!"