Nearly everyone, including star Ryan Reynolds, disliked Green Lantern. Reynolds is actually rather good in it but his efforts were
tragically wasted in a largely dull origin story. Out of the film's many issues, the biggest one was the over-abundance of awful CGI, which ensured that the film felt more like some terrible cartoon than a live-action movie.
Nowhere is this more jarring than in the tedious and soulless finale, in which Green Lantern fights against the main antagonist, Parallax... or, to be precise, an ugly ginormous blob of sub-par CGI that fights against another, smaller blob of sub-par CGI. To this day, it's baffling that Green Lantern had a budget of $200 million.
This finale serves as a good representation of Green Lantern's problems on the whole: bad writing, too many low-quality special effects and not enough excitement or heart.