I have been wondering what is the best plunder building in KAW that I can use as my one building to use, I am a GHT
If you are HLBC then continue on in HF with Elven temples. They aren't the "best" but you need at least one balanced build to make the most out of you allies bonus. If you already have one then the def blding is the best.
Lvl2 stable IMHO, it's 'heavy cavalry' are fearsome, although they are lighter than they're counterparts, 'knights' they can use that maneuverability for an advantage.