You are confusing the anti-matter universe of Qward, which is a Green Lantern staple, with the dimension of Earth-2 (sometimes Earth-3) where the majority of people on Earth are evil-minded, Superman is Ultraman, Wonder Woman is Superwoman, Batman is Owlman, etc. Earth-2 is featured in JLA/Justice League comics.
The antimatter universe of Qward is where Sinestro was exiled to after he was stripped of his Green Lantern power ring and status by the Guardians of the Universe. Qward is populated by the evil Weaponers and Thunderers, who have had a rather constant history since being introduced. The Weaponers are the ones who created yellow power rings for Sinestro, later recotnned into being prototype Fear emotion power rings. Going back and forth from "our" universe to the Qward anti-matter universe always required the person(s) to use their power rings (or other methods) to change their atoms to anti-matter atoms and back again.
Earth-2 of JLA, however, has been done again and again, from from "opposites" of Superman, Batman, and Wonder Woman, to include an "opposite" of Green Lantern, the Flash, Aquaman, etc.
Recently, this "mirror JLA" took over our Earth, but the supervillians were slightly different, actually using the names Clark Kent, Lois Lane, Bruce Wayne, Hal Jordan, etc. Ultraman's powers were not only from anti-Kryptonite, but he had to avoid direct sunlight, as well. This was the "Forever Evil" blockbuster.
So the antimatter universe of Qward is different from the Earth-2 of "villainous" humans.