My first Cryx heavy jack was a Harrower.
It took me hours and hours and hours to get it on its base, and I ended up replacing pretty much the entire hip joint with pins. It hasnt broken yet, but thats mostly because I never take it anywhere.
Second are Nyss hunters, but I cheated and didnt glue on any of the extra bows or scabbards. (Ended up with 20+ spare bits)
Third would be the Behemoth - I custom built his pose, but over balanced it so badly that the top half literally fell off. After it was glued and pinned. He is now a pile of metal sitting in a jar filled with nail polish remover. (REVENGE!! )