When you see abusive content in channels/communities first please make sure that the content is against our Guidelines.
If you would like to report a single post being against our Guidelines just flag this post and it will be then directed to our team of moderators who then evaluate it and make a decision on it. You can find more details on reporting system here: https://jodel.zendesk.com/hc/en-us/articles/208767365-How-does-the-reporting-system-work-
If you would like to report the whole channel/community as abusive please, use our Contact Us form - choose Issue Type: Emergency -> Threat or Harassment and send us a link to that channel/community. Our admins will then check this channel and act accordingly.