Kyle Rayner: He's Peter Parker-lite. I like him well enough in the Johns run of GL and Morrison/Waid's JLA stuff, but the fact that they had to assassinate Hal's character in order to bring him into existence is pretty awful. His comics were full of revisionist BS history about Hal not knowing fear, Hal not learning from his mistakes, Hal was lousy at making constructs, etc. Pretty much indicates that he wasn't that great of a character to begin with if they needed to tear down Hal's character to make him seem interesting in comparison.
The entire Bat-Family of sidekicks aside from Dick and Barbara. I see a lot of people say that Batman's supporting cast members are more interesting than him, but I fail to see how. These little parasites and their teen angst are so BORING. They don't add anything to Bruce's character that Dick and Babs don't already bring to the table, and serve only to smother him. Damian is ok in small doses, leagues better than Jason "I hate you dad!" Todd and Tim "the dullest person on the planet" Drake, but even he is vastly overrated.
On a related note, Barbara as Oracle has been in some great stories, but she will always be Batgirl to me.
All of Brian Azzarello's original characters for Wonder Woman. Zola, the First Born, Lennox, etc. Zola and her baby are just mcguffins, Lennox and the other siblings breeze in and their deaths are treated as serious drama when we barely know them, and the First Born has zero charisma and just shouts his daddy issues to the heavens and bathes in the blood of his enemies. Cassandra was evil for no apparent reason, and we still don't know what her goals were by the end of the run. As a fan of WW's classic cast and villains, these boring ciphers are a slap in the face.