Can Rayquaza,Kyogre and groudon beat eternatus in his true form if they teamed up?

[Pokemaster]

I think they can but will have to go to there most powerful forms.

 

[DawningWinds]

Yeah probably. It has an absurdly high stat total but most competitive-smart people I've seen talk about it say the distribution is nonsense so that's a point against it (I don't understand this part so I am taking their word for it). Plus Groudon and Raquaza can land super-effective STAB hits, and with Air Lock in play Kyogre and Groudon's abilities won't be messing with each other (though I think ideally you'd want Air Lock and Drought out of play since Eternatus will have Flamethrower so the Rain Dance here weakens one of its moves and it doesn't limit Groudon much since it's best for it to focus primarily on ground-moves here for the super-effective hits). Beyond that it probably depends on the movesets and levels of Groudon, Kyogre, and Rayquaza, but in all honesty I'm not sure Rayquaza going mega or Groudon/Kyogre going primal would even be necessary there. Also, keep in mind that while the in-game battle against Eternamax Eternatus is technically speaking 4 on 1, Zacian and Zamazenta could almost certainly take it without the player and Hop despite not having any super effective moves.

 

[Pokemaster]

That is a great point I didn't think if that.