Bruisers are a type of Swampfolk found in Fallout 3's fourth DLC Pack; Point Lookout. They are a deformed version of human, likely due to a mix of Radiation and inbreeding. Bruisers are similar in appearance to Trackers. They can be identified by their different colored shirts, Bruisers are also covered in more blood than Trackers.
Bruisers can't use guns due to their deformed hands. They will attack with either an Axe or Unarmed, either way their attacks can be very damaging to your health. A Bruiser's unarmed attacks are stronger than a Deathclaw or a Feral Ghoul Reaver. Luckily, they are much slower and they don't have any ranged attacks making them easy pickings as long as you keep moving while you attack.