Dell XPS 9440. Worst keyboard I've ever seen on a Dell laptop. I'm not a fan of the MacBook keyboard either, and this is worse. The touch-activated F row makes accidental activations of Delete / Insert too easy. The flat keys are harder to distinguish, making accidental activation of caps lock a common occurrence. It was a work laptop and so fortunately I didn't have to pay for it.
Personally I'd say my most regretted purchase was the Brand New Model F Keyboards "ortholinear" - It's modeled after an ErgoDox but critically both halves are not connected, so in reality it's two separate keyboards. I don't know how anyone could release something so useless for ~$700. I'm sure all of their other offerings are great, however.