You don’t need to take out every guard to get this trophy.
Just equip fists to ensure you don’t accidentally stab him to death, chase him down after you’ve done the 5 guard shot for full sync (which can be done by just turning round to shoot them while they’re chasing you).
and then
to disarm him and take the branding iron. Then beat him to death with it. You are unlikely to have any issues staying alive in this fight even if you leave all the guards next to him alive.