Misdreavus
I didn't originally think that Misdreavus was broken, but now that Krow has left it seems to almost have taken over. Soon after the Krow ban, the Status Eviolite sets were annoying but still fairly easily checked. Then, NP Missy started popping up everywhere and things just went down hill from there. At +2, Missy completely rips through unprepared teams, and even some that are prepared. For example, a fairly common Missy check is Vullaby, but it gets absolutely raped by +2 Thunderbolt, making NP + 3 Attack Misdreavus a bitch to face when using a team that rely's on Vullaby to check it. Ok, so you run a Scarfer to beat LO Missy, right? Well, then you're fucked by Sub NP. It seems as though the only fool proof counter to Missy is Stunky then, which isn't too bad as Stunky's a great Pokemon overall...but wait, fuck, you just got hit by a WoW from a bulky Missy set. I guess what I'm trying to say is the same thing that most people said about Murkrow: It's too versatile. Now, it may not be on the same level of versatility as Krow was, but it's still more than enough to wreak havoc on the entire LC tier. It seems as if a counter to one Missy set is completely neutered / wrecked by a different one, making numerous checks to Missy needed on any one teams, which inevitably leaves you open to other threats that need countering. I believe Misdreavus is the most devastating aspect in LC, even more so than Sun, leaving it extremely ban worthy.
On the topic of Sun, I haven't formulated a complete opinion as of yet, as some of my teams handle it well while others are terribly weak to it. I'd like to listen to other's opinions on the subject, so yes, you guys still have time to convert me!