Hello Hopee,
Here in the States, it depends entirely on the circumstances involved. Between good friends and family members, it could be a teasing thing. For instance, there is about 15 yrs. difference between one of my younger sisters and I, and there have been plenty of occasions when I've called her a "brat" because she had been pestering me so much. In that sense, it's mildly negative, but in a joking way. So, there are no hard feelings. Instead, she laughs and says, "I know
!"
But, I wouldn't advise saying it to someone with whom you're only mildly acquainted.
Have a pleasant day!
Sweet Momma Sue