Yup! ExDeath and Garland and a good chunk of the other Chaos warriors taunt them about it after Cosmos dies.

It is hard to make someone come across as a brat without being a dick. About the only differentiation I can figure out is how people to react to it. i.e. if they roll their eyes and take it good-naturedly, the comment is bratty. If they get angry or offended or hurt feelings, the offender is a dick. It's in the delivery, maybe? Though I think you've hit on a pretty good distinction too, but I'm not sure how you'd be able to differentiate that in writing, since the nuances are so very subtle indeed.

Maybe it just comes down to whether the character is likeable or not! Like how rich and famous people are eccentric, but poor people are crazy!