Dreaming of aggressive bears is considered bad as per dream interpretation and meaning. An old problem that you had forgotten will come back to haunt you. After seeing the dream you should avoid bringing up old issues.
Dream of aggressive bears attacking you or coming after you means you will get into trouble with law. It also means old enemies will become active again.
Dream of aggressive bears and someone you know means people whom you had trusted and had thought will help you in a crisis will ditch you.
Dream of aggressive bears and unknown people means there will be unexpected problems in unknown places. People you had never met or seen will cause trouble in your life.