Sunder is a character deck card in Back 4 Blood that is an Offense Type with Brawn 
Affinity.
Card Ability
Melee hits cause the target to take 20% increased damage for 5 seconds.
Sunder is a fantastic melee damage support that will be most effective on Tall Boys, Ogres, and other mutations with large amounts of HP. One melee hit to an enemy gives the whole team an effective 20% damage buff for 5 seconds.
Pros
- Massive 20% increase to all damage against the target you just hit
- Biggest gains for teammates with big damage builds such as bomb builds or Weakspot builds
Cons
- 5-second duration might be too short in some instances
- No benefit against regular Ridden