Froslass: Ban
It's too good at accomplishing its tasks. I almost always never fail to put down at least one layer of Spikes, paralyze something with Thunder Wave, or surprise kill something with Destiny Bond. When you pair it with Doublade or another ghost, it becomes quite daunting for an opposing Pokemon to Rapid Spin. Defog isn't as common in RU, from what I can tell in my limited time in the tier, so it's not reliable.