After he got the fear ring
Sinestro.
No , Parallax is the villain .
Thaal Sinestro .
I do not think that Sinestro is really bad however he was a Green Lantern but he was selfish, arrogant and power-mad who drive him to be an ennemy, he has even found Sinestro Corps, a supervillain team, but with terrible threates as Atrocitus, or Black Lantern he has allied himself with Green Lantern and returns to evil ways after, then he is a complex character not as Joker or Lex Luthor who are purely evil
Originally green lantern Alan Scott was vunerable to wood that beijg the weakness of his magic based green lantern in the silver age when hal Jordan was created he was made to be weak to the color yellow and that weakness was used by the villain Sinestro a former member of the green lantern Corp... Currently it has been explained that the yellow impurity of the rings was actually a yellow entity of fear known as parallax which is the avatar of the sinestro corp and now the mythology is written so that all newbies have the yellow flaw until they learn to overcome fear at which point the ring can overcome the yellow impurity and be unstoppable it's only weakness then being a charge limitation
With the exception of Alan Scott (who is a different sort of Green Lantern), every Earth-born Green Lantern has been a member of the Justice League at some point, occasionally with overlapping memberships. They are, in no particular order:Hal JordanJon StewartGuy GardnerKyle Rayner
Sinestro.
the colour green
Depends on which one. The original one, unaffiliated with the Green Lantern Corps, is Alan Scott. The original one from Earth is Hal Jordan. The one who took his place for a time, the one with the orange hair, is Guy Gardner. The black Green Lantern is Jon Stewart. And the newest one, with the black hair and big mask, is Kyle Rainer.
I'm not sure how you define better. But personally I'll go with Batman. He's more controlled, causes less trouble (if we're talking Hal Jordan green lantern he becomes Parallax and kills a lot of people), and wins more fights. Batman has and can beat The Green Lantern, was even tapped for a Green Lantern ring once as well as a yellow ring for the Sinestro corps, and is honestly just a much more interesting and developed character. Also Batman is a self made hero and that is something anyone could admire.
It depends on which Green Lantern you are talking about.
green lantern is stronger than ironman because green lantern can make deadly weapons that can destroy his adimantium or green lantern can throw him to space