Mischievous

Mis"chie*vous (mĭs"chē*vŭs), a. Causing mischief; harmful; hurtful; -- now often applied where the evil is done carelessly or in sport; as, a mischievous child. "Most mischievous foul sin." Shak.

This false, wily, doubling disposition is intolerably mischievous to society.
South.

Syn. -- Harmful; hurtful; detrimental; noxious; pernicious; destructive.

-- Mis"chie*vous*ly, adv. -- Mis"chie*vous*ness, n.