OU is just pathetic at the moment. Mega Kangaskhan will be gone in a few days, its ******ed. I used to play a lot of competitive from 2009-2011 but the game just got too fast paced so I couldn't be bothered with it. I'm starting to get into it again but the meta hasn't settled yet so its hard to make a strong team. Pokebank will be the official tier in 2 weeks so that's probably better to play, unless you want to enjoy a few more games without playing against Deoxys and Genesect.
Pretty much, this is the first time I started battling competitively so I honestly have no idea what is good in Pokebank
Kanghaskan is hard, very hard to counter. I find a Ferrothorn with Iron Barbs and Rocky helmet is a really good 1 for 1 if you just need to get that Kanghaskan out of the way.
As long as it doesnt Earthquake a power up punch takes around 30% from each punch which can cut it down to under half, then a gyro ball hits for like 20% or something.
It'll eq next turn but the damage is done
From there priority/choice scarf and youre good, usually costs me a Ferrothorn but its okay.
That being said though, it needs to go to ubers.
I have no idea about pokebank, by the looks of it Thundurs? Genesect and Keldeo are all big features