I have identified two genres that have an awful singing style: post-grunge (Creed, Nickelback, Seether, 3 Doors Down, Puddle of Mudd, Seether, etc.) and pop punk (Green Day, My Chemical Romance, Blink 182, Jimmy Eat World, Linkin Park, etc.). Gee, I think that covers about 50% of the popular music genres between 1995 and 2010, haha! Post-grunge features a lead singer who sounds constipated and has a weird accent that sounds a little southern, but not quite. And pop-punk features a lead singer that just sounds like an angry American 15 year old boy who's complaining about first world problems. Here are a couple of important resources about post-grunge. I didn't bother to look up any resources about pop punk because, well, it's a blatantly obvious style of lead singing. Obvious angsty teen is obvious.
"Shaun Morgan (Seether)- Another one of the elite post grunge crew that have beaten this vocal style to death 20 times over by now. Morgan combines the usual Kurt impression with a touch of Daniel Johns (lead singer of Silverchair). Gotta give him respect for hooking up with Amy Lee though." -- http://www.therockczar.com/misc/top-40-most-annoying-vocalists
"Five Unbearable Singers We Can Blame on Eddie Vedder" -- http://www.nerve.com/music/five-albums/five-unbearable-singers-we-can-blame-on-eddie-vedder