Mischievous
/ˈmɪs.t͡ʃə.vəs/
adjective
Causing mischief; injurious.
Troublesome, cheeky, badly behaved.
“Matthew had a twin brother called Edward, who was always mischievous and badly behaved.”
Synonyms: badly-behaved, naughty, destructive, detrimental, harmful, hurtful, noxious, pernicious