Something I feel like bringing up, even if it may have been discussed countless times here either through myself or everyone else...
iLlama has the perfect point of one simple statement: "Deoxys-A as a Pokémon is not broken in Godly Gift, that is a fact. Deoxys-A gifting its insane stats away, namely the 180 attack stats that go far and beyond other prospective God Pokémon is both broken and overcentralizing." This describes Deoxys-Attack perfect as many people could easily make the argument that "oh, Avalugg with Special Defense hard walls it, it barely does anything and I can recover against Superpower!" But what comes as an issue isn't Deoxys, but everything else.
With the options that Deoxys has for giving stats to others, such as in the Attack slot Mimikyu, which decimates offense with a single hit of invincibility and the ability to run Life Orb, Z-Move, Lum Berry, or even a Focus Sash alongside Swords Dance to rend teams apart; Smeargle, who sits there and shits all over anything (Don't tell me anything walls it, since FakeSpeed, Bonemerang, Sunsteel Strike, V-Create, and everything else exists alongside Shell Smash); Zygarde, which after a Coil or Dragon Dance, has next to no true counters and doesn't necessarily need coverage bar Tarrows and Espeed, as nigh everything will get hit neutrally or super-effectively by it; Dugtrio, which traps any answer you have to Deo-A's assault and will nuke it off the face of the earth, and more niche mons such as Stallbreaker Light Ball Pikachu or Sap Sipper Serp Counter Azumarill, you're a wee bit restricted for teambuilding. This relates to either your Gods or the Pokemon that receive the stats.
No, I don't mean it's IMPOSSIBLE to run things such as Dialga, Reshiram, or other fun gods that aren't often used, or Pokemon such as Attack Sableye (on second thought don't use that), Special Attack Pikachu, or Speed Mimikyu. It's more that its hard to build teams around them when either the stats they give (for the gods), the utility they provide, or even both may not hold up to something that can beat Deoxys-Attack, such as Giratina or Lugia stall teams. RegenCore teams such as Ho-Oh/Tang/Alomomo also do this job, as well as tailored offense, but this doesn't relate to every team used.
Non-Deo Offense can run Mimikyu or Dugtrio in Attack slots with Deoxys-N or Groudon to attempt to have occasional answers to these extremely hard hitting mons, but Mimik dies to either Sunsteel or will die after taking one single hit (particularly from faster mons or some forms of priority) and Dugtrio is horrible after its Sash breaks due to previous damage, Hail, or Rocks. Ninjask with Attack or Special Attack is very likely to outspeed Deo-A threats, but even then Mimikyu and the abundance of Focus Sashes is troublesome. Other fast Pokemon, such as Tapu Koko, Greninja, and Kartana can provide a way to punch holes in their teams, but many Deo-A teams also carry Sticky Web.
Balance can run a few other things. AV Tangrowth with 100/120 SpDef can wall certain special attackers and can manage physical hits, but it gets overwhelmed and can have trouble dealing with strong SE hits, as well as not getting as much spdef on certain Gods like Deo-N, Deo-S, or Groudon. Alomomola does a similar job almost just as well, in addition to Wishpassing, but it can struggle if the Deo-A has a Serperior, Koko, or other Electric/Grass type. AV Ho-Oh can sit in front of Deo and most Special Attackers for quite some time, but the second Rocks are on the field it's about fucked. SpDef Buzzwole can bunker down against almost anything besides Fairium nukes and Deo-A itself, and with 120, 154, or even the rare 230 SpDef it can take most hits fairly well, but also requires you to run Buzzwole and likely lose a ton of momentum on switchin. Ditto also exists, which also can be used on Offense, but have fun dealing with Mimikyu and Focus Sashers.
So, now we've got a good list here. Offense has Mimikyu, Dugtrio, Ninjask, Koko, Greninja, Kartana, and a few other fast mons, and Balance has Tangrowth, Alomomola, Ho-Oh, Buzzwole, Ditto, and a bunch of other mons. I can't go list everything since I myself don't have the best of experience with the meta. Stall is also an option, with Lugia/Giratina/Giratina-O/Ho-Oh being viable options as gods there.
...Doesn't that sound a bit boring? I don't know if its just me, but I don't see too much variation I can use here. With Deo-A as the undoubtedly most popular God (Popular =/= Needs ban, but keep reading) before this (In a tournament of roughly 16 players, every match I had, including Grands, was Deo-A, and most of the matches I had to watch while waiting were Deo-A), preparation for it was a necessity rather than a 'want'. You couldn't run into the field and expect to win using just your favorite mons getting buffed through your favorite Uber. If you did so, Deo-A would come by and snatch you up and fling you away, teaching you a lesson in the process. I don't need to truly 'prepare' for any other Hyper Offense-based Gods in this regard, but instead can just run your regular answers to those such as Priority, Hazards and Hazard Control, and Pivot moves. Stall is the same way; I don't need to prepare for Giratina Stall exclusively, then worry about Lugia Stall, Ho-Oh Semi-Stall, and then Shuckle. Instead, just running a stallbreaker if need be or a hard hitting setup mon is all that's necessary.
Deo-A kind of ruins games by that. You have to prepare for it and it alone, as if Deoxys-Attack teams are their own archetype of team you must prepare for. No other god forces you to do that, as well as no god provides as much utility in a single slot (imo) than Deoxys-Attack. You don't get an offensive nuke, Spiker, Taunter, good Lead/Wincon, all in one slot.
[[[[TL;DR: Deoxys-Attack makes everyone prepare for it which none of the other gods even come close to doing, so its annoying as hell.]]]]
yay for ranting. plsdonthurtme