Pokémon Ferrothorn

[Sleepwalkah]

Ferrothorn only has two weaknesses and lots of resistances, so it can set up easily as soon as its counters are off the field. It may be the slowest thing in the whole metagame but after a +2 or even +3 boost noone likes to switch into this hitting and phazing terror.
The point is: everyone thinks he can take out Ferrothorn by constantly dishing out neutral special attacks to get rid of it in 2 turns. But the 1-2 turns it can last longer due to the full SpD investment make the difference.

 

[Firebird101]

Ferrothorn has only two weaknesses and lots of resistances, so it can set up easily as soon as it's counters are off the field. It may be the slowest thing in the whole metagame but after a +2 or even +3 boost noone likes to switch into this hitting and phazing terror.

The problem is that fire and fighting are very common attack types and since Ferro is so slow it needs a lot of support to pull a sweep which is undesirable when there are so many better sweepers who pack more punch and have much better speed. Granted it can threaten pokes with t-wave but after using curse it can be safe assume it doesn't have that so other pokes who don't like to be paralyzed like Gengar have much easier time finding a opportunity to switch in burn it which forces it's teammates to give it even more support, heck, they practically have to gift-wrap it for Ferro. The idea is cool but the reason why Clefable works better is cause you can't wear it down or cripple it with statuses and it's weaknesses are much less common.

Ferro is a support mon with a decent attack power so it doesn't become a total setup bait and it is best to use Ferro as such. Your Ferro set may catch some people off-guard but I highly doubt it is hard to defend against and it'll just be a deadweight.