I'll address the repeatedly aspect of your question. This suggestion will not work for one-off incidents or after the fact.
Stack Exchange has functionality in place to block spam and/or abusive content coming from the same source. It exact workings are secret but it is known as SpamRam. Regular users and mods have a few ways to indirectly interact with SpamRam. One most noticeable is raising a Spam flag on a post. After 6 spam or R/A flags the IP address of the original poster is put into SpamRam, effectively blocking them from accessing the network from that IP address. The block expires after a while but repeat offenders will see longer block times going forward.
While reviewing a suggested edit reviewers can choose the first option in the reject dialog:
Spam or vandalism
This edit defaces the post in order to promote a product or service, or is deliberately destructive.
when two reviewers pick that option, not only did you stop that edit from going through, you also added the IP address of the user behind that edit into SpamRam.
So if you have a case where a single entity is repeatedly suggesting harmful edits and these edits are easily recognizable you could organize a rejection mob in a chatroom and instruct the reviewers for these kinds of edits to pick the Spam or Vandalism reject reason, effectively blocking more of such edits coming in in the short term.
Before you consider this route do consult, involve and obtain permission from your site moderators as, in general, chatrooms with organized moderation power tend to spiral out-of-control when not governed correctly.