About Mega gyarados, Beedrill, etc

===Mega Beedrill  =======

Pokémon type: Bug / poison

When Cresselia is in raids, it’s a good time to mega evolve a Mega Beedrill. Its bug moves are strong against psychics, and it will boost other bug type Pokémon in the skirmish.

The best Pokemon Go Mega Beedrill counters are Shadow Mewtwo, Mega Charizard Y, Mewtwo, Shadow Moltres, Shadow Metagross & Shadow Ho-Oh.

Mega Beedrill has a max CP of 3824, with the following stats in Pokémon GO: 303 ATK, 148 DEF and 163 STA. Mega Beedrill's best moves in Pokémon GO are Poison Jab and Sludge Bomb (21.94 DPS).

===Mega Gyarados =======

Mega Gyarados is a Water and Dark-type Pokemon, instead of Water and Flying like regular Gyarados. The Pokemon’s typing now means that Fairy, Electric, Fighting, Bug and Grass-type moves are all super effective against it.

https://www.dualshockers.com/mega-gyarados-weakness-pokemon-go/

There are a few top counters to Mega Gyarados in the game, let’s take a look at them.

Mega Venusaur is the undisputed king of Mega Gyarados Raids. Mega Beedrill is another effective Mega Pokemon. In terms of Electric Pokemon, there are a few solid choices. Zekrom is the cream of the crop here. Magnezone, Zapdos and Raikou are also strong counters. Another solid counter is Electivire. Alongside the Electric-types, there are a few good Fighting Pokemon. Lucario, Conkeldurr, Machamp and Breloom all shine here.

• Mega Venusaur – Vine Whip/Frenzy Plant
• Mega Beedrill – Bug Bite/X-Scissor
• Zekrom – Charge Beam/Wild Charge
• Magnezone – Spark/Wild Charge
• Zapdos – Thunder Shock/Thunderbolt
• Raikou – Volt Switch/Wild Charge
• Electivire – Thunder Shock/Wild Charge
• Lucario – Counter/Aura Sphere
• Conkeldurr – Counter/Dynamic Punch
• Machamp – Karate Chop/Dynamic Punch
• Breloom – Counter/Dynamic Punch 

===Mega Steelix =======

Mega Steelix Counters

Pokemon Go Mega Steelix Raid Guide, best counters and moves

https://www.gamesradar.com/pokemon-go-mega-steelix-raid-counters/

• Mega Blastoise Water Gun and Hydro Cannon
• Mega Charizard X or Y Fire Spin and Blast Burn
• Mega Slowbro Water Gun and Water Pulse
• Mega Gyarados Waterfall and Hydro Pump/Aqua Tail
• Mega Houndoom Fire Fang and Flamethrower
• Mega Lopunny Low Kick and Focus Blast/Fire Punch
• Rhyperior         Mud Slap and Earthquake
• Garchomp         Mud Shot and Earthquake/Sand Tomb
• Groudon                 Mud Shot and Earthquake
• Mamoswine         Mud Slap and Bulldoze

===Mega =======

Mega Houndoom Raid Counters

                Pokemon                   Moveset

• Mega Blastoise Water Gun and Hydro Cannon
• Mega Gyarados Waterfall and Hydro Pump
• Mega Lopunny Low Kick and Focus Blast
• Mega Aerodactyl Rock Throw and Rock Slide
• Swampert         Water Gun and Hydro Cannon
• Rhyperior         Mud Slap and Rock Wrecker
• Tyranitar          Smack Down and Stone Edge
• Rampardos         Smack Down and Rock Slide
• Conkeldurr         Counter and Dynamic Punch
• Kyogre                 Waterfall and Surf