ALRIGHT ladies and gentlemen I had to get real creative for this one!

Garchomp @ Groundium Z
Ability: Rough Skin
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Swords Dance
- Earthquake
- Rock Tomb
- Substitute
This never-before-seen sub + groundium z tech allows garchomp to beat zard x reliably, as zard will have to either mega evolve or non mega outrage to break our sub, both options ensuring the win for garchomp. Tapu Lele dies to the z move 93.75% of the time, and we can safely 2hko aggron as it is not carrying avalanche.

Tapu Fini @ Tapunium Z
Ability: Misty Surge
EVs: 248 HP / 104 Def / 156 SpD
Calm Nature
IVs: 0 Atk
- Taunt
- Nature's Madness
- Brine
- Icy Wind
If the sub garchomp tech wasn't enough for you, then I present the most heat Tapu Fini you've ever seen. Calm Mind Tapu Lele is ordinarily an impenetrable wall for slower special attackers, but Z-Nature's Madness allows us to bring it down to 25% in one turn! Icy wind into brine will ensure the ko from here if Tapu Lele attacks t2, and Fini survives a +2 Shattered Psyche thanks to Misty Terrain if they cm again instead.

Altaria-Mega @ Altarianite
Ability: Pixilate
EVs: 232 HP / 104 Atk / 72 Def / 100 SpD
Impish Nature
- Dragon Dance
- Giga Impact
- Cotton Guard
- Roost
Last but certainly not least, hybrid dragon dance + cotton guard Altaria Mega Edition is my final counter to the team. Its unique dragon/fairy typing allows it to naturally wall Mega Charizard X, and its high special defense allows it to live any attack from Tapu Lele and KO t2 with +1 Giga Impact.
An ordinary dd altaria, even with Earthquake, would 50/50 Aggron between Heavy Slam or Head Smash. Alas, I am shit, and I would surely lose this 50/50. Thus, our altaria packs cotton guard and roost despite being a dragon dance set, allowing it to safely cotton guard t1 and survive a Choice Banded Head Smash even in non-mega form. From here, Altaria can safely roost and eventually knock out aggron with two (2) +3 mega evolved Giga Impacts.
This was a difficult team to break, and I really had to pull out the heat for this one. These might be some of my most creative sets yet! Hopefully I'll find something more standard before the week ends, like maybe a Riolu or smth.