LOL busted.

 The worst breakage I've ever had was a Royal Albert tea set I purchased from a lovely elderly woman in the UK. This despite her boxing it up superbly in a large box, everything was secure with plenty of bubblewrap & cardboard inserts.

The seller did two things wrong though, firstly she didn't label the box as fragile, and secondly she tied a rope around all four sides of the box meeting in the middle of the top in a big loop/bow that made it very convenient to carry it. The rope 'handle' worked great, but it also led to the box naturally swinging as you carried it, which was apparently too tempting for someone handling it as they had obviously let it 'fly' when it reached it's apex. One bottom corner was complety stoved in, and everything in a direct line through the centre of the box between that corner and the opposite top corner was broken beyond repair.

 Guess what company delivered it?

Hmmm in retrospect I suppose that makes 'three' things the seller did wrong.