Since this thread is a bit dry at the moment i have decided to start a discussion.
Hoopa-U is something that was brought a lot in this thread earlier as a candidate for being suspected (By no means that's my final opinion at the moment so don't reply calling me ban hungry). At that time it was decided that it was too early to talk about Hoopa-U since it was just released and needed the meta needed time to get more stable. Well now a lot of time has passed and the meta has became more stable so now is a good time to discuss about this magnificent pokemon.
Why its so powerful?
The thing that makes Hoopa-U so powerful is its stats and movepool, which combined make it really unpredictable. There's no way predicting what set its running so there's
never a safe switchin. The moveset can vary from Choice Scarf, Life Orb, Steel Breaker, Choice band, Choice Specs, Nasty Plot, etc.. You get the idea. This reminds me of Genesect which was banned for similar reasons. Hoopa-U's movepool is really wide and it can in theory cteam types such as Water, Ground, Flying etc.
Stats
Now lets look at its stats
HP:80
Attack:160
Defense:60
Sp. Atk:170
Sp. Def:130
Speed:80
The first thing that people usually notice is its monstrous Attack and Special Attack which make it a strong wallbreaker. The thing that most people don't notice though is its that nice Special Defense which again is a huge help
in crucial matches. Even though it's Speed and Defense kinda make it easier to kill its still a cannon with a nice special defense.
Few fun calcs about its bulk:
252+ Atk Choice Band Entei Extreme Speed vs. 0 HP / 0- Def Hoopa Unbound: 221-261 (73.4 - 86.7%) -- guaranteed 2HKO
252 SpA Gardevoir Moonblast vs. 0 HP / 0 SpD Hoopa Unbound: 242-288 (80.3 - 95.6%) -- guaranteed 2HKO
Psychic: Hoopa-U has had a huge effect on psychic. Since its release Psychic has gone up in the usage stats and why shouldn't it? Now with the addition of Hoopa-U psychic doesn't really have any outright bad match-ups. (Maybe dark if it has Mega Sharpedo/Mega Gyara and Bisharp but thats why Colbur Slowbro is invented c:) The offensive core of Hoopa-U, Victini and M-Gardevoir handle all the weaknesses well. Hoopa-U takes care of Ghost, Victini handles bug and M-Garde puts some great offensive pressure to dark. And if you dont use Hoopa-U, You will surely loose Psychic vs Psychic match-ups. I wouldn't be suprised if Psychic would overtake Flying as the most used type soon.
Dark: For Dark Hoopa-U brought huge amount of coverage. Gunk Shot makes the Dark vs Fairy match-ups a lot more easier and Psychic STAB can just almost walk through poison and makes battles against fighting a lot more easier. Also the addition of Energy Ball can ease up the Ground/Water match ups. If you aren't using this on your Dark team you're insane.
I don't have a clear opinion on Hoopa-U (Part of the reason why im bringing this discussion here). It's Typing, Movepool, Stats and Unpredictability make it a force to be reckon with and you can never have a safe switchin against it. On the other hand again, it's lack of speed and awful defense make it easier to be killed by faster pokemon and priority. Is it broken? i don't know to be honest. One thing is sure though.. its one of the best pokemon avaible to use in monotype at the moment.