Naughty is similar to mischievous. We usually use it with kids when they do something they aren't supposed to or cause trouble in some way. It's generally used in a negative way. I've never said it to an adult. If you do hear someone say it to an adult, they are using it more in a funny (sometimes sexual) way. Since it can come across as sexual, I'd advise not to use it with adults. Mom to son: "I told you not to eat anymore cookies! You are such a naughty boy! (Perhaps the mother would say it in a joking way.) Dad to daughter: " The babysitter said you were very naughty today. Why didn't you listen to her? "(This would be said in a more serious tone.) Maybe it's similar to 淘气/调皮 in Mandarin.

It is a word you would normally use to describe an unruly or disobediant child It is often used to describe mildly bad behavior. Nothing that is so bad that it can be considered evil, bt rather bad actions that are mischevious in nature.