Source: comicvine.gamespot.com

8. Legion

The Guardians of the Universe are jeeeeeeerrrrrrrrrks. Like, mega-jerks. They are the worst. And here is but one of the many, many, MANY instances of them screwin' up so bad that Hal Jordan and the other Green Lanterns of Earth had to step in and fix s**t. Again.

Once upon a time, there was a planet called Tchk-Tchk in sector 407 that was inhabited by a race of angry bugs. They started to exhibit conqueror tendencies, and the Guardians figured they should put a stop to that. So they had some Green Lanterns seal their planet away, leaving the Tchk-Tchk to"¦starve to death and die out. This is called "genocide".

The creatures invented one thing to be their method of survival: the Soul Jar. The Soul Jar enabled the creatures to mix their minds into one giant suit of armor, which escaped the Lanterns’ seal on the planet and went on a murder spree. Legion, as it was now called, killed the Green Lanterns of sectors 2817, 2816, 2815, and 2814. That last one was named Abin Sur. Sur's replacement, Hal Jordan, showed up and beat Legion down so FRIGGIN' BAD he never really showed up again.

But I like him so he goes on the list.