Ferrothorn is a pretty decent check/counter, depending on the moveset. Grass and Ghost are not very effective to it, and as the ability poll decided against immunity or limber, it is susceptible to Toxic and Thunder Wave. It does, however, has an issue with fighting or fire type attacks.
Forretress is another one that resists stabs,but dislikes fire. It can set up a round of hazards and use Toxic to prevent it from being complete set-up bait.
As said by others before me, Skarmory takes anything that's not a fire attack like a boss. It too can set up hazards, phaze with whirlwind if it sets up or toxic it/Brave Bird it in the face.
Jirachi takes CaP2's stabs easily, but doesn't like fire either. On a Rain team, Jirachi will counter/check CaP2 pretty good, because Jirachi doesn't realy care about fighting type attacks anyway.
All the above fear fire attacks, which means if it goes for a moveset with a sketched V-Create or Sacred Fire, Heatran will wall it to no end. It will also punish it with STAB super effective fire attacks. However, Heatran is heavily hindered by Rain. It's attacks will lose half their power in a bang. Heatran is therefore not perfect. Then again, perfection is not necesarry. The likelyhood of someone using CaP2 in Rain with a fire attack is also very small.
Hydreigon is another pokemon that doesn't care about fire, but it's afraid of fighting type attacks. Mach Punch will be available through Sketch, but I asume there will be relatively few stat boosting moves to go with that. Hydreigon can threaten it with STAB Dark Pulse or Fire attack in the sun.
Dragonite is the one true counter to this thing. Multiscale is quite posibly the best ability in the game, and Dragonite's usage stats in regular OU seem to show what it does for a pokemon. Even with something like Ice Punch or Icicle Drop, CaP2 will fail to ohko. It will be outspead after a quick Dragon Dance and suffer from Outrage or Fire Punch in sun.
Gliscor has been popping up in the comments, and I agree that it can use Toxic/Fling/Ice Fang on CaP2 and then heal back through Poison Heal and Sub/Protect. I hate that set in general, and I think it will serve as a good check to CaP2, but lacking a great way to fight back outside of Ice Fang makes me weary. If you go for an annoying Gliscor anyway, you might allready run Toxic anyway.
Scizor does a fair job at punishing CaP2 too, with Choice Band U-Turn into Heatran or something like that, it can actually give CaP2 a run for it's money. As does actually anything with U-Turn and decent attack (Landorus, Mienshao, Darmanitan and Zapdos all learn U-turn, have good attack stats and can outspeed CaP2).
This is what just pops up when I see the stats of CaP2 and the pokemon that can serve a roll other than pure CaP2 counter.
EDIT: I just came up with a good one: Salamence. It has Intimidate and resists Grass and Ghost. It will suffer heavily from any Ice attack, but it outspeeds CaP2, so when it's in, it can threaten CaP2. Crunch, Fire Blast or Fire Fang will do some good damage. I don't have calcs yet, they might come later, depending on my schedule.
