Even the word "bully" isn't strong enough. "Bully" is a diminutive term that sounds like it describes an unimportant/childish problem. (The word originally meant "lover" or "friend" in Dutch.)
When the target is an online community, I use the term "attacker" in the infosec sense.
When someone sends threats, I think the best term is "harassment."
> The word originally meant "lover" or "friend" in Dutch.
That doesn't seem very relevant though; modern day Dutch language speakers have absolutely no such association with that word — the word it came from is not in modern use and is unknown to most. Only a dedicated linguist would recognize the Dutch etymology of 'bully'.
I think "attacker" and "harassment" are both accurate but I feel that they are too clinical/adult/long/abstract for people to get angry about. You want words that a 5-year-old understands, and you want words that conjure an image.
When the target is an online community, I use the term "attacker" in the infosec sense.
When someone sends threats, I think the best term is "harassment."