I'd like to say some things since we've gone and did so much of a large post about it. But in my personal opinion, even though I've used Eternatus Eternamax alot, and I am a fan of having a million sets on it due to it's incredible viability. I don't think people truly understand why it's so good to begin with.
Eternatus-eternamax, which is this giant thing, is in of itself not that good, actually.
Now, its stats are monstrous and there's no denying that it's the best Pokemon. But this is Pure hackmons. Being the best Pokemon, doesn't mean that you're the most viable.
To begin with, allow me to explain in full this time, why eternamax works so well.
Obviously -- the first part is the stats. Defenses through the roof, a speed tier equivalent to Mewtwo's. And attacking stats that are passable (Being above the par of 105 that is needed.) with a 115 attack and a 125 special attack, allowing it to, unlike other walls, be able to put decent offensive pressure against everything. Even without a shell smash.
The main reasons of why it's so good, and why stats matter this time, unlike what I've said before, is thanks to 3 main factors of Pokemon Sword and Shield, being Neutralizing gas, Dynamax and, well, Wobbuffet.
The first two are rather self-explanatory. Neutralizing gas allows Eternamax to bypass Wonder guard, not get hit by prankster sleep, avoid damage from huge power over muscling it as well as break through Fur coat, Ice scales, Sturdy and other longevity sets designed not to get hit. It also disables any attempt at cheesing with No-guard OHKO, poison heal recovery, or contrary offensive setup against it. This gives it a very, very big advantage that often goes unnoticed in regular play and shafted as "Well, Eternamax is just good".
To put this into example, we'll use a fellow helping Pokemon to illustrate our point.
I present to you..
Chansey! Everyone's favorite and most annoying pokemon in Generation 7 itself. Chansey being the most famous user of Imposter, alongside sets with Fur coat, phazing and stealth rock and baton passing that allowed it to sit there, eat hits on anything that dares attempt to take time to sweep, and overrall be a nuisance.
What I want to focus on here is chansey's bulk. Eternatus eternamax is what you get if you took a chansey, shuckle and a Dragpult, then threw them together in a blender. Making a fast, bulky and very defensive pokemon. So, if that was the case, then obviously, this pokemon should be able to do everything the above mentioned 3 can do.
But, that isn't actually true. Eternatus Eternamax suffers from 2 things, it's poison typing and its lackluster speed.
I know I said that Eternamax has great stats and presence, so you're wondering why I'd go back on that. And the reason for this can be seen in the very sets Ransei has put forward, and many others, with the Psychic-meta game that now is ever present in pure hackmons thanks to this Eternamax threat. The power level of a pokemon becomes so important and so large in order to constitute a sweep that most of the time, anything capable of taking down eternatus, is capable of taking down everything else, too. But this is pure hackmons. A ninjask has one of the shittiest stats in the game, but it is still one of the main threats. And everyone knows this, because in pure hackmons, its not the overrall validity of the pokemon that matters, it's the niche you can pull off with them.
Ninjask runs many sets. Comatose Whirl-wind being the main one, seconded only by No-guard OHKO and Neutralizing gas rocks and nuzzling. Made to disrupt the enemy's attempts at moving.
Generation 8 doesn't have that many pokemon, that is why I believe pokemon home and the expansion DLC will improve pure hackmon's viability rankings and most certainly bring Eternamax down in usage. Eternamax can in of itself deal with it's own counters with the right set, it's the best pokemon, after all. A game of prediction is how pokemon has always worked. But, I still believe that Eternamax here is only really so viable, and so strong, and so used.. because it's an exploit in what we're used to.
You already know why Neutralizing gas is good, why shell smash sweeping is viable and why being a defensive monster makes you setup easier. So much so that just the niche of being normal and Psychic-type despite the horrible stats makes Indeedee one of the best sweepers in the game with it's taunt, shellsmash, stored power and blue flare. Unlike Eternamax, who can run earthquakes and bolt beaks for better coverage due to it's actually decent stats.
But you don't know why Eternamax is so good. We've always had shell smashers, we've always had stored power mons, and even in generation 8, with such a low count of mons that gives Eternamax such a fearsome presence, almost as if we're back to generation 1, and as you send out your alakazam, you opress everything else because you're just better, and the amount of Pokemon is not enough for you to be offset-ed and be forced to use something else.
Eternamax is so good. Because of the final part. "Wobbuffet". Eternamax on Pokemon showdown, cannot be impostered.
This is huge, stupidly huge. Balanced hackmons will show you, both in generation 8 and generation 7. Our fluffy chansey, and the infamous wobbuffet are one of the biggest counters to any attempt of setting up that you can think of. It does not matter one bit what on earth the enemy is running, because I'll just copy it with a choice scarf, and win anyway. Even in Pure hackmons back on Gen 7, chansey was never not seen.
Imposter allowed people to simply disregard what the enemy has planned. No need for prediction on wether it's running bolt beak or blue flare to send out my zacian or Mandibuzz. No need to guess if you need to spectral theif or haze. Whirl wind (Or as Gen 7 would have it, heart-swap. But heart-swap is not in Gen 8, further giving Eternamax that alakazam opression feel due to the simple lack of options against it.).
But. Eternatus Eternmax, for some ungodly reason, cannot be impostered even without neutralizing gas. Even if you sat there and clicked transform, it will simply fail. And honestly, this is what makes it what it is now in my eyes. Because if you could copy eternamax, not only would eternamax itself start running imposter to pick off potential niche sweepers, but mons capable of using transform as a last ditch effort would make sure to keep it on just in case. It is true that Neutralizing gas supresses transform in the first place, but imagine the previous calculations provided by Ransei with transform.
Zacian crowned lives +3. But nothing else does. They say it should not run calm because it loses speed and becomes useless, but isn't that a chansey conundrum? If Zacian could click transform at the cost of being slightly useless, copy a +3 eternamax, and straight up counter-sweep. You can turn the tide of an entire game just using that. No imprison spectral theif longeivity, no dealing with "Hm, what set is this?". This would not only force eternamax to be alot more scared of just setting up blindly at any chance the opponent gives you, but it may even force itself to make sure to run taunt, which expends one of the four move slots that eternamax so begrudgingly values. Pokemon like Necrozma dusk mane and Mel-metal would also find a small niche in being able to counter eternamax this way, thanks to their type bulk and overral decent enough defensive stats (Although melmetal gets blown away by stored power at +3, but you know, focus sash niches and stuff. Better than surviving and just going "shit uhh I think I have haze, atleast I won't get COMPLETELY DESTROYED").
But what confuses me about it, is honestly that this hard-coded anti-transformation sounds a bit buggy to me in terms of considering that this is pure-hackmons. Here's a video of ditto being used to transform into eternamax via the prospect of hacking. I am aware that using transform in the big raid battle against it in the main-storyline of darkest day will have transform fail, but pure hackmons goes under the premise that this is pokemon that you can hack into the game into your party, and use. And seeing that if in doing so.. this happens. Then I would imagine imposter/transform should function as seen.
I have no real evidence and I am not fully prepared for an argument about it, and I don't know if it's even been brought up before. But as far as can be seen here (At 1:39 in the video). Ditto transforms into it.
Obviously this isn't the actual eternamax but who cares. Eternatus normally at x3 is just as good if not better than eternamax thanks to it's higher special attack. Special attack that when copying an Eternamax from, can even one shot zacian and everything else Ransei pointed out as a range for eternamax that it ever so struggled for. If this was how the game functioned on the ladder, people would be terrified of using Neutrailzing gas Eternamax setup so freely, because you'd risk having the opponent turn into an even stronger version of the one you setup with. One that didn't give a single point of interest about wether or not you were calm nature. Focus sashes would be more common, so would be rocks, and the meta-game would slowly but surely expand from there with the chansey plague that was ever present before.
Ofcourse, I am not saying that this is a good thing. Personally, I used chansey alot in Gen 7, but I never said I liked it. But this is important to remember when considering what mons are actually viable, and why. Eternamax isn't just good because it has the best stats. It boasts something no pokemon can ever hope to replicate. Even better than normal-type spectral theif immunity, or dark-type prankster immunity. It boasts a hard-coded imposter immunity.
It would be interesting to see a Pure hackmons (No neutralizing gas) tier in my opinion, and should the eternamax be impostrable in this case, pokemon home and the DLC would make pure hackmons possibly even more diverse than the cluster fuck Gen 7 Balanced hackmons and Pure hackmons was before. An Eternamax having imposter turns it into a worse pokemon due to it losing so many stat points, but it does allow it to preform even when it could not transform, unlike what chansey suffered beforehand. Chansey could only wall.. but eternamax, assuming ng is basically like having no ability for both sides, just like in generation 1, can preform and sweep, not just wall.
In conclusion, Ransei is gay and should learn not to post replays from the very start of the meta cause I wasn't as good back then. Thank you for coming to my ted-talk.
Also Zacian S tier with eternamax it's just facts man.