This is for ZA and the Mega Dimension DLC. Some Pokemon are changed between the two, these are mentioned. They also don't have the level they learn their moves at, as they're gonna need to be high 80s minimum (excluding Gourgeist who already has its only needed move when you catch it)
"Chompy" Mega Feraligatr
Aqua Jet (lv.21) -> Liquidation (lv.40/TM)
Bite (lv. 10) -> Crunch (lv. 36)
Dragon Claw (TM) / Outrage (lv. 56/TM)
Ice Fang (TM) / Earthquake (TM)
(To tell the truth, I used Emboar instead of Feraligatr, but it was kind of redundant, so I put my first playthrough starter instead.)
Liquidation and Outrage are STAB and Mega STAB. Ice Fang or Earthquake hit one of your two un-mega'd weaknesses, and Crunch is kind of the only other good physical move it gets, but it is a solid follow-up attack if your opponent survives the first hit.
"Bois" Mega Heracross
Pin Missile (Lv. 10) -> Megahorn (lv. 45)
Brick Break (lv. 24)
Aerial Ace (lv. 15)
Rock Blast (lv. 28)
You get this from a trade that is essential already, you just need a Pikachu from Wild Zone 3. Even if it wasn't already overlevelled from the traded Pokemon EXP boost, its Mega's monstrous 185 Attack nukes everything in front of it, once you get it from Quasarctico after Main Mission 10. Just use this; you'll see what I mean.
When you start the DLC, you'll want to swap this for:
"Cuddles" Annihilape @ Shell Bell
Rage Fist
Drain Punch (DLC TM seller)
Shadow Punch / Claw
Bulk Up
A Fighting Distortion with Mankey is almost guaranteed when you first get to enter them, due to the small pool of distortions at the start. Just change the time of day if you don't get one first try.
"Cuddles" is here for one thing. Beat up the Rogue Megas as quickly as possible. Bulk up, tank Rage Fist stacks, then heal it back up with 350 BP, +1 Attack, supereffective (we'll get to that later) Plus Rage Fist.
Mega Absol (Z)
Night Slash (lv. 27)
Slash (lv 23) / Play Rough (TM)
Shadow Claw (TM/lv. 40)
Swords Dance (lv. 20)
So... it's also mandatory to get a level 30 Mega just for doing the easiest boss battle you'll ever face? Thanks! This quickly sweeps Trainers such as Gwynn in the main storyline, and revenge kills with short-charging moves. Then, they just give it a BETTER Mega in the DLC? One that has no charging on any of its moves at all? Thanks!
"Drilllllllll" Mega Excadrill
Metal Claw (move reminder) -> Iron Head (TM)
Dig (lv. 28) -> Earthquake (lv. 46)
Swords Dance (lv. 36)
Drill Run (lv. 40) (DLC -> Rock Slide if keeping)
You get Drilbur at Wild Zone 8, and evolve it shortly after, when it gets to lv. 31. This solos all 3 matches with Canari, easily. And 2 of them are BEFORE it can Mega Evolve! Fun fact, max friendship in ZA boosts critical hit rates, so, if it likes you, Drill Run crits half the time!
However, in the postgame of the main storyline, before the DLC, this is outclassed by (spoilers):
"Zee" Mega Zygarde
Extreme Speed
Earthquake
Thousand Arrows
Core Enforcer
Yes, this is a legendary. But is just so darn good, I can't not mention it! A priority, area, and sure-hit move on one Pokemon is invaluable for destroying Poke Balls and Mega Crystals in Hyperspace, thus speedily completing tasks. If that weren't enough, if you're in a pinch, don't worry! You'll go 100% form, Mega Evolve, and nuke with 200BP Nihil Light!
Since I need an alternative, just stick with Excadrill, with Rock Slide over Drill Run. Warning: it will save you an hour before the DLC, but lose you three during it.
Mega Gardevoir
Psybeam (lv. 18) -> Psychic (lv. 38)
Draining Kiss (lv. 12)
Dazzling Gleam (lv. 30) -> Moonblast (lv. 49)
Mystical Fire (lv. 44) / Calm Mind (lv. 35)
Don't worry, you can still get this pretty easily even after the Mystery Gift! Head to the little grassy area east of Quasarctico to find a guaranteed Ralts. After a bit of training, and a (slightly late) Mega Stone at Quasarctico, you have a monster of a special attacker.
"Gulp" Mega Victreebel
Toxic (Alpha move)
Razor Leaf (lv. 10) -> Power Whip (lv. 44)
Poison Jab (lv. 30)
Leech Life (lv. 33)
Lots of these only get good moves /Mega stones late on in the game. This is because the early game is trivialised by a combination of Bois and Gulp. You can get this as a Wild Zone 5 Alpha at lv. 22. It then evolves immediately by level, then again by a pretty cheap 5000P Leaf Stone at the Stone Emporium, giving you a level 22 BST 490 beast when the trainers are level 15! You want to keep this for its useful panic button of Toxic, where Alphas and Megas alike die no matter your level while you stall them out with the switch-in clock.
Only swap it out temporarily when you have the DLC Rogue Mega Battles, because then you want:
Gourgeist @ Focus Sash
Trick-Or-Treat
That's it.
Spawns as an Alpha in Wild Zone 13 daytime. Focus Sash from postgame Racine Construction, so you don't need to level this up and can still take a hit to get a move off. Use ToT on the Rogue Mega. Switch to Annihilape. Win.
Thanks for reading my essay!