Campaign: Kun-Lai Summit

The non-timerunning version of this achievement is Slum It in the Summit, so there are 10+ years worth of helpful comments on that page if you are looking for missing quests.

I was having an issue with this, stuck with The Thunder King and Zouchin Village parts.

Went and found the Pandaren on the beach of Zouchin Village and completed everything up to the funeral and the questline ended abruptly with still no completion for that area on this achievement. I went to the page for Slum It in the Summit to read comments and try and figure out the issue.

First, I had the A Witness to History quest in my log with the Vale gates still unopened, and one comment noted this can cause phasing issues, so I went and completed that real quick.

Then, I realized I still had the It Was Almost Alive quest from Lorewalker Cho which wasn't indicating anything on the minimap. I believe you need to have his chain completed as a prerequisite to Zouchin Village, so go back to the area for this quest and summon Cho with The Tongue of Ba-Shon, and continue with this questline. This will lead to completion of The Thunder King portion of this achievement.

After this, you'll be led to Zouchin Village with a quest to ride a hot air balloon down to the village. At this point, you'll be able to complete the Zouchin Village quests and receive the Kun-Lai campaign achievement.