Gonna leave my thoughts on Mega-Kanga, and I'll just say that this big mama makes almost every other OU Pokemon look like complete pussies in comparison.
Mega-Kanga has the following qualities:
1)
Power - There's no denying Mega-Kanga packs some great strength, she's basically has a Choice Band backing up every one of her attacks, while giving her the freedom to switch moves. Her STAB even packs a very solid 102 BP, which can hit a majority of non-resists for clean 2HKOs, such as "
252+ Atk Parental Bond Kangaskhan Return vs. 252 HP / 252+ Def Rotom-W: 153-180 (50.32 - 59.21%) -- 75.39% chance to 2HKO" without any sort of boost at all, and she can lay a heavy beatdown or outright KO on most physical walls after a boost.
And then there's this:
252+ Atk Parental Bond Kangaskhan Return vs. 4 HP / 0 Def Garchomp: 279-328 (77.93 - 91.62%) -- guaranteed 2HKO
252 Atk Garchomp Outrage vs. 4 HP / 0 Def Kangaskhan: 196-232 (55.68 - 65.9%) -- guaranteed 2HKO
Garchomp, known as a premier offensive tank of a Pokemon (or at least in earlier generations), is outright showed up by Mega-Kanga's tanking prowess. Many other offensive Pokemon simply do not stand a chance against Mega-Kanga one-on-one.
Also, while this doesn't really qualify as "power", Parental Bond Seismic Toss is a consistent '200 HP damage' on any non-Ghost: this 2HKOes almost every offensive sweeper as well as any max HP wall with <100 Base HP.
2)
Bulk - This is the next biggest thing Mega-Kanga has got going for her: she is more than capable of tanking a hit while gearing up for a rampage, and also makes her very resilient to priority. This makes Mega-Kanga very difficult to revenge kill in general, making it that much harder to stop Mega-Kanga from plowing through your team. To put this into perspective:
"252+ Atk Landorus-T Superpower vs. 4 HP / 0 Def Kangaskhan: 312-368 (88.63 - 104.54%) -- 31.25% chance to OHKO". That's 240 BP coming from positive-natured 145 Base Attack, and it still has less than a 50% chance for a KO (It has no chance at a KO if it isn't Adamant!). Any less, and don't even hope to OHKO it.
3)
Speed - While not overwhelmingly fast, she does outspeed pretty much any defensive Pokemon and even some offensive Pokemon such as unevolved-Lucario, Excadrill, Mega-Garchomp, Zygarde, and Landorus-T. She is also the primary reason why Talonflame would want to invest that much more into Speed.
4)
Coverage - Having Normal as your main STAB is pretty great when the user hits hard enough to make a name for itself, since this means there are only a few holes left to patch up. In the case of Mega-Kanga, she gets perfect neutral coverage with just 3 moves via Normal + Fighting + Dark. The open moveslot can be teched against potential Kangaskhan responses without drastically affecting its general matchups, which is also what makes her such a threat.
5)
Boosting move - Wanna know how to make a potent sweeper even more deadly? Give it an option to further boost its power! Many sweepers are not overwhelming or even great due to not having a method to actively boost their power, such as Jolteon, Starmie, Gengar, Staraptor and even newcomer Greninja. Kangaskhan has a +2 boosting move that just so happens to serve as its coverage move, and she also has the bulk to pull it off against a wide variety of targets. How very damn convenient, eh?
6)
Priority - The saving grace to Mega-Kanga's lack of breakneck Speed. This move, combined with her aforementioned bulk and power, makes the prospect of revenge killing a Mega-Kanga safely a whole lot more daunting. Revenge killers to Mega-Kanga are usually Fighting-types, and even then +2 Parental Bond Sucker Punch can deal 40-50% to
Terrakion, and that is pretty scary when applied to any frailer, non Dark-resistant Pokemon.
Take a long look at those traits, and you'll recognize those as attributes
literally every offensive Pokemon would kill to have, as in saying "
why the hell would you want anything else??". No doubt Mega-Kanga can be played around, but Mega-Kanga stands out as a Pokemon with an incredibly lopsided 'risk-reward ratio', and can easily screw up an opponent
just because they do not know what your free moveslot is, which Kanga will always have space for. People who haven't gotten swept by Mega-Kanga thoroughly have probably gotten lucky regarding its coverage option, myself included (if those Mega-Kangas stop carrying Earthquake in favor of Fire Punch, I'm f**ked).
Before one talks about Sableye, remember Mega-Kanga has 5 partners to work with as well, such as the likes of Volcarona or maybe Rotom-H who don't give 2 flying shits about Sableye, which can result in matches where it is not so much 6v6, but a back-and-forth war of attrition between Mega-Kanga and Sableye; with Mega-Kanga looking for an opportunity to steamroll, and Sableye trying to stop Mega-Kanga from going crazy.
Agreed with
Chou Toshio, Mega-Kanga would be / is pretty overcentralizing and not healthy for the meta.
