Rtj could be a person's initials or a nickname. Maybe they would beat someone to a pulp if they were in a really angry situation, like if they were being attacked or if someone had seriously wronged them. But without more context, it's hard to say for sure.
Well, 'rtj' is quite a mystery here. The phrase 'beat em to a pulp no fiction' sounds very aggressive. It could be that rtj is part of some sort of a rough crowd or a person with a lot of pent - up anger. Maybe in their world, violence is seen as a way to solve problems. However, it could also be a bluff and rtj might not actually be as violent as the statement makes them seem. There could be a backstory where they have been pushed to the limit and this is their way of expressing their frustration or a warning to others not to mess with them.