Higher Pokemon, OU Strength

Aegislash

 * High Stats are 125 instead of 150.

Arceus Forms
I'll do this one later, this could take a while.

Blaziken

 * Attack stat is 115 instead of 120.

Blaziken-Mega

 * Attack stat is 155 instead of 160.
 * Ability is now Big Pecks instead of Speed Boost.

Darkrai

 * All stats are lowered by 20 except for HP.

Deoxys

 * All stats are now 90.

Deoxys-Attack

 * Attack and Sp. Attack are now 150 instead of 180.
 * Speed is now 90 instead of 150.

Deoxys-Defense

 * All stats are lowered by 10 except for HP.

Deoxys-Speed

 * Attack and Sp. Attack are now 90 instead of 95.
 * Speed is now 160 instead of 180.

Dialga

 * HP and Speed are each lowered by 10.
 * No longer has the moves Flamethrower, Thunderbolt, Ice Beam, and Aura Sphere.

Genesect

 * Speed is now 90 instead of 99.
 * Can no longer learn the moves Blizzard and Blaze Kick.

Gengar-Mega

 * Ability is now Unnerve instead of Shadow Tag.

Giratina

 * HP is now 110 instead of 150.
 * Attack and Sp. Attack are now 70 instead of 100.
 * Speed is now 50 instead of 90.

Giratina-Origin

 * HP is now 110 instead of 150.
 * Defense and Sp. Defense are now 70 instead of 100.
 * Speed is now 50 instead of 90.

Greninja

 * Hidden Ability is now Hydration instead of Protean.

Groudon

 * Attack, Sp. Attack and Defense are each lowered by 40.
 * HP, Sp. Defense and Speed are each lowered by 20.

Groudon-Primal

 * Attack and Defense are each lowered by 40.
 * Sp. Attack is now 100 instead of 150.
 * HP, Sp. Defense and Speed are each lowered by 20.

Ho-Oh

 * Hidden Ability is now Weak Armor instead of Regenerator.
 * Attack and Sp. Defense are each lowered by 10.

Kangaskhan-Mega

 * Its Ability, Parental Bond, is changed so that the first hit is just as weak as the second hit.

Kyogre

 * Attack, Sp. Attack and Sp. Defense are each lowered by 40.
 * HP, Defense and Speed are each lowered by 20.

Kyogre-Primal

 * Sp. Attack and Sp. Defense are each lowered by 40.
 * Attack is now 100 instead of 150.
 * HP, Defense and Speed are each lowered by 20.

Kyurem-White

 * All stats are lowered by 10.

Landorus

 * Ability is now a new ability called Inner Ineffectivity, which prevents the user's accuracy from being lowered when Sandstorm is active.
 * Hidden Ability is now Defiant instead of Sheer Force.

Lucario-Mega

 * Ability is now a new ability called Strong Aura, which senses the target's EV spread just like Frisk senses the target's item, however, there is a 50% chance of one of the user's stats lowering by one (including accuracy and evasion) after it senses the EVs.

Lugia

 * Ability is now a new ability called Poor Armor, which is just Weak Armor except it affects Sp. Defense instead of Defense.
 * Defense and Sp. Defense are each lowered by 10.

Mawile-Mega

 * Ability is now Strong Jaw instead of Huge Power.

Mewtwo

 * Attack, Defense, Sp. Attack, and Sp. Defense are each lowered by 10.
 * HP is now 86 instead of 106.
 * Speed is now 105 instead of 130.
 * No longer has the moves Fire Punch, Fire Blast, Thunder Punch, Thunder, Ice Punch, Blizzard, and Avalanche.

Mewtwo-Mega-X

 * Ability is now Pressure instead of Steadfast. However, it doesn't work right after Mewtwo mega evolves.
 * Attack, Defense, Sp. Attack are each lowered by 20.
 * HP and Sp. Defense are each lowered by 30.
 * Speed is now 105 instead of 130.
 * No longer has the moves Fire Punch, Fire Blast, Thunder Punch, Thunder, Ice Punch, Blizzard, and Avalanche.

Mega-Mewtwo-Y

 * Ability is now Pressure instead of Steadfast. However, it doesn't work right after Mewtwo mega evolves.
 * Attack, Sp. Attack, and Sp. Defense are each lowered by 20.
 * HP and Defense are each lowered by 30.
 * Speed is now 105 instead of 130.
 * No longer has the moves Fire Punch, Fire Blast, Thunder Punch, Thunder, Ice Punch, Blizzard, and Avalanche.

Palkia

 * HP is now 70 instead of 90.
 * No longer has the moves Flamethrower, Thunderbolt, Ice Beam, and Outrage.

Rayquaza

 * All stats are lowered by 35.

Rayquaza-Mega

 * All stats are lowered by 35.

Reshiram

 * Attack is now 50 instead of 120.
 * Defense is now 70 instead of of 100.

Salamence-Mega

 * Ability is now Weak Armor instead of Aerilate.

Shaymin-Sky

 * All stats are now 100.

Xerneas

 * All stats are lowered by 5 except for Attack.
 * Attack is now 91 instead of 131.

Yveltal

 * All stats are lowered by 5 except for Attack.
 * Attack is now 91 instead of 131.

Zekrom

 * Sp. Attack is now 50 instead of 120.
 * Sp. Defense is now 70 instead of of 100.