I like the covers for both Green Lantern #51 and Green Lantern Corps # 45. Both feature a fallen Green Lantern going against his team mates/allies. In the case of GL #51, it’s Hal Jordan as Parallax versus the bunch of new Lanterns from the emotional spectrum.

greenlanternandglc

GLC on the other hand, shows Guy Gardner in his Red Lantern form taking on his GLC team mates and allies. Fortunately, both Green Lanterns revert back to normal by the end of their respective books.  Oops.  Should have added a spoiler tag.