Originally Posted by Chuck Anstey
4. More time needed to be spent showing that Sinestro became disillusioned with the Guardians and the power of will after being wiped out by Parallax and yellow energy, when he previously was an absolute true believer. There is a kernel of a really believable reason why Sinestro wanted the one ring, I mean the yellow energy ring for himself but they needed to show more of the transformation and his desire to control what he thinks is the most powerful energy in the universe. Plus if they spent some time and played up the fact that Sinestro was the number 1 GL right up until Hal Jordan, a human newbie, beat Parallax by himself so maybe Sinestro isn't quite the leader and as powerful as they all thought he was and jealousy could have been an additional factor. Obviously Hal Jordan could control green energy better so maybe yellow energy would give Sinestro the edge he needed. Show it please. As it is shown, Sinestro's faith in the power of will should have been restored by Hal Jordan so his taking the ring makes no sense.
I don't know about the movie, but in the comics, Sinestro has absolute faith in the power of will - his own.
He started off as a very respected GL. Sometime during Hal's early career and training, they happened to go by Sinestro's homeworld, where there were GL flags flying EVERYWHERE. Seems that at home, Sinestro was more a dictator with major control issues (and a major cult of personality) than a policeman; his fellow citizens displayed the flags not out of gratitude, but out of absolute fear of Sinestro and his ring.
When the Guardians found out about THAT, that was bye-bye for Sinestro's career as a GL. That's when he went and acquired the yellow ring (or brought out one that he had previously acquired in secret). Much, much later came the Sinestro Corps. Sinestro has stated on various occasions that the Guardians and the Green Lantern Corps do not have the will to do "what needs to be done" to establish order in the Universe, but that he does. Even if the creatures he uses are all psychopaths with power rings.
Having Sinestro give up the green ring because he "lost faith in the power of will" (rather than because his dictatorial and control freak nature was found out, or because he lost faith in the Guardians) doesn't make sense.