This achievement is gained by completing the “The Blood Hunter Hunts” dungeon (Temple of the Jaguar). The blood hunter is the main boss of the dungeon. This achievement can also be gained by defeating him in a daily event dungeon, if you can’t progress far enough in his dungeon.
For the fight, focus mainly on him as the Jaguars he spawns in will keep coming back until he’s dead. Once you get their attack patterns down, you can parry them for more stamina. If you’re set up decently he shouldn’t be too bad.
Honestly I suck when it comes to these types of games but if you can get a good run, or a good weapon/relic then you should be good to go. The weapon that worked best for me was a whip, since the charged attack interrupted most enemies and let me get a few more hits in on most of the enemies.