Borderlands 2
69 Achievements
1,625
63-84h
Went Five Rounds
Completed Round 5 of any Circle of Slaughter
25
How to unlock the Went Five Rounds achievement in Borderlands 2 - Definitive Guide
Many of the arenas have an opportunity to redo the final wave (or equivalent eg murderlins arena in the tiny Tina dlc). In this case you can import a character who popped this achievement, do the final wave again and...
*pop*
I actually got this on the 360 and then in the xbox one version completed wave 2 of an arena in someone else's game and it popped.
It is possible to do this on any playthrough, and if you have trouble early on, you can always return to Normal once you're in True Vault Hunter Mode, for example.
Here are some videos of me completing all 5 rounds using my Siren, Magda.
The Circle of Slaughter can be located in either Ore Chasm or The Fridge areas. Simply head here to receive the side mission "Hyperion/Bandit Slaughter: Round ..." from the Innuendobot 5000 or Fink.
The Circle of Slaughter has the same concept of Moxxi's Underdome DLC from Borderlands. You're placed in an arena and then presented with waves of enemies that you must defeat until you complete the round. So for this achievement, you must get to and complete round 5. Once a single round is complete, you can head back to the quest giver to hand that round in and gain some XP/Cash as well as restock on things.
Trying to do this solo can be a little tricky, but the Circle of Slaughter in The Fringe is a a little easier because the levels are set lower. If you feel you need a team but don't have anyone that is up-to-par who can help, ask HERE.