Guild Wars 2

Killed the last one but the achievement did not pop out. Attached a screenshot of the specific location of the Karka and the missing achievement due to the bug.

You may have confused one of the other White Crane Terrace locations with the missing one:

White Crane Terrace Explore the cavern where the skritt buys your globby purple stuff.
White Crane Terrace Peer down at the boulders where the ledges are diverse.
White Crane Terrace Hop high in the diverse rocks.
White Crane Terrace The Priory’s bed bugs prefer bunks.
White Crane Terrace Search near the skritt’s subterranean rowboat.
White Crane Terrace Squeeze into stony confines near the door to the dominion.
White Crane Terrace Stop and smell the flowers between the magisters and the memorial.

According to Dulfy, you are in the wrong spot. http://dulfy.net/2015/06/23/gw2-lions-arch-exterminator-achievement-guide/

Good luck.