Abyss Anglers: Myths from Beneath

The 4th time I killed [npc=262103] it threw me 3 pieces of meat. Each counted as a kill. The 4th kill counted as kills 4, 5, & 6 and got the achievement. The very next kill I got 3 pieces of meat again, then 2. It appears to be random.

A frustrating achievement.

As of posting, the only Mythic target is Champion of Pahk. You'll need to kill this 6 times for the achievement.

However:

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• The boss starts with 99 scales, which is not straightforward to solo within one dive, even with the max breath and trips to both of the air vents ( /way 67, 26, /way 65, 18)
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• If you complete this with other players, there is a significant chance that you don't get credit at all either because you've had to surface and it has been killed in the meantime, or simply because it doesn't reward credit sometimes (please see this comment for a potential fix here, but I've not managed to make it work)
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My best advice is to get all the upgrades and then do your best to solo it during a quiet period, at least until Blizzard fix the lack of credit sometimes. Circle the boss while killing it, try not to stop moving to avoid getting caught by the sharks.

If you spam the spear button you can get several catches per kill.