Nicalis is a dev/publisher, and why do everyone hate them?
I don't quite know actually.
The only things that I know that they have/are working on are Cave Story +/3D and Binding of Isaac: Rebirth.
Perhaps it's because they took Cave Story and ported it 3 different times?
Acquiring the rights to Cave Story (Pixel no longer has a say in what happens with it)
Using those rights to shut down fan projects, like the DS port, Cave Story stuff in Indie Brawl, and youtube let's plays. All stuff that Pixel was always fine with or had even explicitly given his OK or helped with (providing source code etc.)
This is probably the source of most of the hate.
Botching the release of Cave Story Wii (glaring sound bugs were left in for 8 months, lol. Replaced the pro translation by Shih Tzu with an amateurish one with pop culture references
The whole Night Sky debacle. Nifflas was making Night Sky for PC (like all his previous games, where he and all of his fans expected it), was told after signing the publishing rights away that it would be a Wii exclusive, which got delayed, eventually fell through and much later it was finally only released for instead PC anyway)
Dropping the release of La-Mulana Wii in North America and Europe without even informing Nigoro. http://la-mulana.com/en/blog/report-2.html
The list goes on.