It looks like fears. Well not fears more like nightmares, but like the riddle says, they are the results of a wish. So maybe these are the unexpected outcomes of wishes?

But why are the two groups separated? I can't figure that out at all. At first I thought there were two outcomes to every desire, but I couldn't justify that. I'm sure that thing about fear gas is pretty important.

My guess is we have to find the 'why' or 'who' behind each clue... but I've got no clue.

Samuel L. Jackson follows you everywhere and keeps on zapping you.
This tells me someone wanted to be in an action movie, or wanted  Sammy Jack as a sidekick. But that doesn't seem very helpful without a who. Maybe one outcome is connected to another?

It's possible that we need to separate the actual ends of desires from the fear gas desires. Suddenly I'm sure that's it.

** SPOILERS **
This post will reveal the entire worked solution to this riddle.  If you're still working on it, stop reading here!

The Riddler tells us that this one is about “making diverse people live their nightmares” – all the easier because “every fear is really the end of a desire.”  Indeed, each of the clues sounds like a nightmare, or at least a wish gone horribly wrong.  But what to do with them?

Well, we could make a big intuitive leap, guided by these observations and perhaps by the clues' mention of Wakaba and Movie!Akio.  Or we could just plug any of the clues into Google.  The clues each return just two hits.  One, of course, is this thread.  The other is IRG's Corrupt a Wish thread.

Corrupt a Wish is a game in which one player makes a wish and another grants that wish in a perverse way.  We can Google each of the clues to figure out what wishes produced each of these nightmares.  For example, Googling the first clue yields this exchange:

dollface: I wish there was an interesting place in this town I could go to.
Prince_of_Stars: Granted; it's a dominatrix's house.

Now, what to do with this?  First of all, are we supposed to focus on the first player (the wisher) or the second player (the genie)?  Well, it's the first player who's being forced to “live their nightmares,” so that must be whom we're concerned with.  After all, it's their “desire” that's being corrupted.  So let's get the wishes that go with the first eight nightmares.  They are:

dollface: I wish there was an interesting place in this town I could go to.
Tamago: I wish I had a lot of money.
Seitokaichou: I wish I was a Jumper.
Nanami's Rose Groom: I wish all the hot lesbians on IRG were straight.
OnlyInThisLight: I wish there was a law against playing the same five songs over and over again on the radio.
Iris: I wish I had more motivation for arts.
BioKraze: I wish I were a cat.
Epi_lepsia: I wish I was a boy.

But what is “the end of a desire?”  The Riddler is very literal-minded, and we might guess that he literally means the last letter of the wish.

We can test that guess.  In order from first to last, the eight wishes in the first group would give us the letters OYRTOSTY.  That doesn't seem very helpful.  But maybe the letters are just out of order.  In fact, this is the case.  All we need to do is put the wishers in alphabetical order (“as easy as ABC”) before taking the last letter of their wishes.  For instance, BioKraze's wish comes first and ends with T; then dollface's, ending in O; then Epi_lepsia's, ending in Y, and so on.  In sum, these eight wishes give us TOYSTORY, and we know for sure we're on the right track.

We repeat on the next group, which contains nine clues.  Their associated wishes are:

Anji: I wish I could unsee the movie se7en.
KissingTKiryuu: I wish I could read people's thoughts.  Nonsense ooweeooo
Tamago: I wish I could see ghosts and spirits.
Emiemipoemi: I wish people would appreciate theatrical Sweeney Todd, not just gush about the film.
Aine Silveria: I wish that I had more physical stamina.
MissMocha: I wish I had enough money to buy dinner.
Kaelyndra: I wish that I could teleport.
BioKraze: I wish that I were way smarter than Miki.
Imaginary Bad Bug: I wish that I knew someone who was just like Wakaba.

Using the same process on these wishes – alphabetize by wisher and take the last letter – gives the word ANIMATORS.

We now have TOYSTORY ANIMATORS.  This leads straight to the riddle's solution, PIXAR.