I know you all would immediately jump into this and say (TAKEN FROM TF2!!!), yes it is taken from TF2 but I think something like that could work in DB. I’m pretty sure Fragger has specific lines pointing towards Thunder so why not other mercs with each other? Phoenix could argue with other medics that he’s the best, Red Eye snarking at Phantom etc or Proxy getting her payback to Aimee… have some interactions here and there.
This is just a comedic thing that you won’t pay much attention to, we already have a Revenge and Domination medal but they don’t matter for a team-based game like DB.