Something popular despite (and because of) widespread negative reception
“Notorious” is certainly a fine word for describing “a piece [. . .] that has gained popularity through negative reviews or appraisals”. I would also consider use of related terms like “guilty pleasure”, “kitch”, “(something) we love to hate”, or “so bad it's good” depending on the material and context. There's also the term “cult” to describe these sorts of pieces (esp. “cult classic”) or their followings.
If you have some space to explain yourself, you might consider coining “the Regretsy effect” which you could describe as the curious phenomenon of explosive sales after a craft posting was criticized on the (now defunct) crafting ‘lowlight’ aggregator.
Antonym for “rave”
1. Commentary on available options
— — Verb — —
“Pan” is used a lot, but I hear and read it much more often as a past-tense verb (not a noun), e.g.:
The film was universally panned by critics.
Ebert panned the film, decrying its sympathetic portrayal of a violent protagonist.
— — Adjective — —
If the word describes “review”, I think you're better off using “very critical” or “scathing”, c.f.:
I read a scathing review of that movie.
I read a rave review of that movie.
— — Noun — —
In that example, “review” could be taken out of the latter, and it would still make sense as a noun:
I read a rave about that movie.
If your desire is a replacement for that usage, there isn’t a great one-word substitution. “Pan” is fine, but is less recognizable:
I read a pan of that movie.
You might be better off just forcing the verb in that case:
I read a panning of that movie.
There's also “(a) rant”, but that is difficult to recognize outside of collocations with “rave”.
2. My suggestions
It's not a single word, but as far as noun phrases go you might consider “hit piece” as in:
“Did you read the A.V. Club review of Howard Cantour.com?”
“Yeah, basically a hit piece.”
This has lots of problems itself, and is basically a metaphorical usage of the primary definition that has more to do with politics and is very similar to “smear campaign”. It also adds in a bit of negativity about the review, possibly conveying that the person using this term believed the review was overly harsh or resorted to ad hominem.
If you can trust context to communicate that you are talking about a review, you might just go fully metaphorical and say something like:
Ebert's evisceration of Transformers comes as no surprise to anyone who knows his opinion of Michael Bay's characteristically baroque usage of CG.
There's also “takedown”, for which you probably won't find much dictionary backing (I couldn't) but might be useful in its modern usage (such as seen here).