worst Transformer toy of all time...

I'd probably say Supreme Cheetor, can't speak from personal experience as I didn't follow Beast Machines (didn't get into it, and probably would have left TFs were it not for RiD) but that toy failed on so many levels.

Probably characterised by the fact that I once went into one of the Toys R Us near where I live looking for Energon figures, and there were still one or two Supreme Cheetors sitting on the bottom shelf.