There's a karp reskin for the Holy Mackerel, which displays an intentionally humiliating bold "FISH KILL!" text in the kill feed for everyone to see. With a name tag, you can also rename it to whatever suits you. That's all I know thus far.
I really hate the people I am forced to work with sometimes. Can't wait to get home for July 4th for a few days.
PS - If you ever have the chance to go to Jacksonville, North Carolina, do yourself a huge favor and don't.