The grumblings over Sinestro facing off against John Stewart instead of Hal Jordan in Justice League got me thinking.
Sinestro and Hal Jordan are absolutely archenemies. Sinestro was Hal's friend and mentor and he betrayed him. Sinestro has fought Hal Jordan more than anyone else. He even secretly infected him with the Yellow Impurity to warp him into a villain and destroy his life. These two guys hate each other.
John Stewart married to the late Katma Tui, who was Sinestro's protege and replacement as GL of Korugar. John and Sinestro have fought many times over the past several decades. Immediately prior to Emerald Twilight, Sinestro had also infected John and used him to murder his friend Ch'p. That's cold. John is single-handedly responsible for placing the Green Impurity into every ring within the Sinestro Corps, thereby nerfing the entire army that Sinestro had built. Sinestro is absolutely not a fan of John Stewart right now.
Guy Gardner suffered brain damage and was in a coma for years because of Sinestro. In turn, Guy beat down Sinestro and stole his yellow ring. Guy Gardner does not like Sinestro and the feeling is mutual.
Kyle Rayner exposed Sinestro's greatest scheme when he learned what Parallax really was. As payback, Sinestro murdered Kyle's mom and infected him with Parallax to use as his latest puppet. To add insult to injury, Kyle then started dating Sinestro's own daughter, Soranik Natu. It's safe to say that Kyle and Sinestro despise one another.