These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
It's not just funny, it's likely the reason they asked him to take on the role.
Ho Yay: Sinestro and Abin Sur have this in spades.
Iron Woobie: Laira. She discovers that her father has been massacreing his enemies, and is forced to fight him in order to put a stop to it. Even though she wins, she is still helpless to stop him from killing himself in the hopes of regaining his lost honour. All things considered, she holds up very well.
Les Yay: There's something ever so slightly suggestive about the way Arisia and Laira smile at each other.
Nightmare Fuel: The Shadow Demons. What they do to a Green Lantern at the start of the film is nothing short of horrific.
Abin Sur not believing Atrocitus when he tells him that Sinestro is fated to become a universe shattering enemy of the Green Lantern Corps - the unwavering faith Abin has in his long time friend just makes the knowledge of what Sinestro eventually becomes that much harder.