I agree with
@Seek, there are a LOT of bad vapes out there based on manufacturing and design issues.
To really find the worst vape, I think it fair to not deal with a re-branded item and base complaints on basic design. For me, a "worst" vape was the Gpen elite. It is/was a Grenco model that was designed by them rather than a rebrand.
It is like the IQ in that it has a great form factor, precise temperature, conduction oven heating. It worked pretty good too--the first time. The secret is keeping the mouthpiece clear. A near impossible task with the mouthpiece screen just above the oven. If one were to not grind and keep the herb in larger pieces, it might be a pretty good vape. For me, that thing was toast in a first week. If one were meticulous in regular cleaning, it might not be a bad vape. If you are one who wants to run through a couple of ovens before peeling it apart to clean, probably not so much.