[jayrox]

I'll tell you what worked for me:

I walked over the bully and told them to their face that I did not appreciate the way they were talking to me. That I will not accept or tolerate being treated the way they were attempting to treat me. I then wrote an email to their manager with what happened, copied the conversation that was had in chat and explained that we are adults and that behavior was not acceptable. Their manager had a talk with them and it hasn't happened again.

I was/am prepared to forward my communication to HR if the time comes where they try to bully again.