Huh, this looks really bad. Ultra League level Giratina bad.
Currently, the Great League does not suffer from the dominance of single pokemon the way Ultra League suffers from Giratina. And it seemed that it should be able to avoid that danger due to the sheer number of viable pokemons there. Even Giratina wouldn't cause as much havoc, as the Great Leauge has a decent number of usable counters - Azumarril, Wigglytuff or even Mawile.
But, enter Deoxys Defense. Being a pure Psychic and having access to Counter and two very powerful charge moves - Psycho Boost and Rock Slide - gives it super wide type coverage that hardly any counter can slip within.
Looks like the only viable counters will be Ghosts (with some possible secondary typing), as no Dark pokemon will stand a chance against Counter, while some Bugs might get into rough parity against Rock Slide, but Deoxys' DEF might still prevail.
Well, Giratina could help, but if Deoxys arrives first, we might see a lot of Dusclops, Spiritombs and maybe Alolan Muks just to stay alive.
I was actually considering using Dusclops. I hatched a perfect Duskull and at level 36 its CP tops out at 1500cp.
An aside, this still isn't the ideal IV spread for Great League Dusclops. An a/d/s spread of 7/15/15 will cap at 1500cp at level 40, giving it the most bulk it can have for Great League.
Hmm, how so?
It's got the fast charging Infestation and Crunch and Aqua Tail both with very good spamming capabilities. There seems to be something very weird with gamepress TDO calculator, as it lists the horrible Poison Sting higher than Infestation, and for Infestation it has the same DPS/TDO for every charge move, suggesting that somehow those don't get activated at all in PvP.
However, I've found another surprising counter - Gliscor or Gligar (Gliscor arguably better, as it has Earthquake as opposed to the horrible Dig).
Not really bad, just a major player in the meta.
Viable counters include Metagross, neutral to Counter, resists Rock Slide, doubly resists Psycho Boost, and can hit with Meteor Mash, Scizor, neutral to Counter and Rock Slide, resists Psycho Boost, and attacks with the SE Fury Cutter/X-Scissors combination, and Forretress, same resistance profile as Scizor, hits with Bug Bite/Heavy Slam (STAB on both), with a better PvP stat profile (DEF heavy).
One will have to plan for this, but it won't break the meta, just bend it some.
Yes, because it has Counter as a fast move and doesn't totally rely on spamming charges like Cresselia does. Any steel-type utterly walls Cresselia, D-D will destroy these with Counter spam alone. Cresselia is also efficiently countered by several dark types, some of which need a shield for Moonblast, but are otherwise super favored. Again, Counter destroys the monotype darks and hits hard on the dark/poisons even if they have shields.
Cresselia isn't a great starter in my experience and can lose to several good pokemon even in the later game. Deoxys-D will be a great starter and has fewer counters, I fully expect there to be some metagame shift when it gets released if it's as good as it seems.
