Thread necromancy and double post in a single post, yay!
I can't decide what keyboard is actually the worst, so here are many keyboards in different categories:
Worst keyboard I use on almost daily: HP PR1101U.
Rubbery, flimsy, stiff, ISO. 500g of plastic. Feels like typing on breast implants. Very dry and hollow breast implants. The desk vibrates when you type on it. It's fairly responsive, as if you don't need to mash the keys everytime I press a key. You can't use it as a weapon. And it's not even that cheap (20 bucks retail price).
Honorable mention: Genius KB-110X. Same as above, but it's horribly spongy and is actually reasonable priced (only 200% the manufacturing cost, instead of 500%)
Worst keyboard I have at home: A4Tech KD800L. It's a chiclet (or at least the chiclet clone where there are no key stabilizers. Speaking of key stabilizers - after a year of use the Enter is the wobbliest I've seen. It's like 5 degrees when you look at it wrong. And 10 degrees if you type on it.
Worst keyboard I've ever laid my hands on: Tie between some brandless wireless keyboard, an Apple Wireless Keyboard and. The first is cheap, flimsy and feels like typing on an actual kitchen sponge. Kitchen sponge covered in rubber. AWK is expensive, kinda study, feels nice to type on... but I can't type on it because it's a chiclet.
Honorable mention: Post-2014 Razer Blackwidow, because someone at Razer thought that a linear ear buster (Razer Green) is an amazing idea.
Honorable mention: Logitech K120. If it weren't for the actually quite good typing feel, I'd not recommend it to someone who "just wants a keyboard" and shelling out 30 bucks for a Masterkeys Lite L is too much for him/her/it. Flimsy build quality (as in light and all plastic, but at least it has actual screws in them) and still quite expensive (20 bucks for ISO model because everyone and his mother complains about ANSI),