The worst scene for me to render was (still is) the hospital scene where camera dollys through a waste amount of appearing cranes. The reason for that is that Simon Butler instead of animating the cranes with one same reference which he could simply intsance to get more copies...actually duplicated the crane within reference folder several times and after that also within scene. This means that every new object has its own texture, which (beside the enormous polgon count) made scene so wast that it is constantly collapsing, even if rendered with render farm. I was trying to render it for more than a week. e also didn't stay clear with naming the objcts, which made the thing even worse for me to arrange renders and adjust glow on the objects!
Also I have to mention that all the scenes I have received from no matter whom weren't clearly named and arranged (despite my request for it in annual plan and meetings) so it was a great nightmare for myself to do anything further in them.