History of Blood Will Have Blood

Blood Will Have Blood is a triumph: "Land the final blow on the Guardian who last defeated you." It tracks "Medals earned".

How to complete

• The text is a revenge kill: after a Guardian defeats you, defeat that same Guardian before you die again.
• The closest documented match is the Payback medal, described as "Before you die again, defeat the player who last defeated you" in the Gambit medal guide. Destinypedia's medal list defines Payback as "Defeat the enemy who killed you last."
• Practical tips: note the name of your killer in the killfeed, stay near your team, and hunt that player instead of re-engaging blindly. In Gambit the killer is often an invader, so respawn timing matters.

Unconfirmed

I could not open a source stating which playlist counts the medal, which seal it belongs to, or any reward, so none is claimed here. That the triumph counts the Payback medal is an inference from the matching wording, not a confirmed fact.