

The 5th gym was probably the easiest gym fight since the 1st gym on Insanity.
So, alot goes on between gyms 4 & 5. The boss fight with Shadow Admin Marlon, gaining the ability to mega evolve (even though you can't even use it on your starter at this point, unless you chose Metagross) as well as gaining the option to change your Pokémon's nature, before going to the Ruins Of Void and fighting all 3 legendary beasts, Raikou, Entei, and Suicune, back to back to back with no heals in-between before fighting Ho-oh & Lugia back to back, again with no heals in-between, before returning to where it all started, the shadow base. I honestly didn't switch up my team that much as I only added two Pokémon to my arsenal. I added a Froslass, who somehow was the only Pokémon I had that could not only out speed shadow Marlon's Zapdos but also take it down immediately, if it didn't activate its quick claw. It's also effective against both Aegislash & Dusclops as it can out speed both & hit them with special effective damage. I ran it special attack & speed, but if you're raising it up right from the day care, you could easily run this thing Attack & Speed as it gets so many good physical attacks if you evolve it immediately after hatching it, like Iceicle Crash & Crunch, and it's attack stat & special attack stat are the same.
I also added a Eelektoss as I needed a strong eletric type & wasn't about to raise a Elekid, when I know I can get a free shiny one later in the game. This helped a lot as it's another Pokémon that can learn Brick Break, which is essential for this game with dynamax battles, and is effective against Marlon's Tentacruel, Sharpedo, no matter how you train it, and/or Aegislash, & Dusclops, if you trained it physically with it being an electric Pokémon that can also learn the move Crunch. I ran it special, as Thunderbolt is just simply more effective than Thunder Punch. It's only like a 10 point difference when it comes to Special Attack & Attack, so it's good either way you run it. Eelektoss is also insanely effective against Maxima's Empoleon, as it can tank a Wave Crash, even after it's used Swords Dance. That said, they were both absolutely useless in the 5th gym fight. Eelektoss did nothing to anything & Froslass either got eliminated instantly by Raichu or Manectric. So, I brought the team you see above.
All Pokémon were IV & EV trained.
Metagross - 252 Health & Attack - Adamant Nature.
Zygarde - 252 Heath & Attack - Adamant Nature.
Sharpedo - 252 Attack & Speed - Adamant Nature.
Steelix - 252 Health & Defense - Relaxed Nature.
Mismagius - 252 Special Attack & Speed - Modest Nature.
Gengar - 252 Special Attack & Speed - Modest Nature.
It was a double battle & I ran Metagross & Zygarde to lead things, hitting a double Brick Break on Klinklang, eliminating it on turn one. His Raichu used Rising Voltage on Metagross who tanked it & then sent in Manectric, who came in burnt. I hit a bullet punch on Manectric with Metagross before Raichu hit another Rising Voltage on Metagross, eliminating him. Manectric then hit a hidden power on Zygarde, who lived and returned the hit with a Break Swipe, which hit both Manectric & Alolan Raichu. I then tossed in Gengar who immediately got hit with a Rising Voltage by Alolan Raichu & got eliminated while Manectric hit another hidden power on Zygarde. I then hit another Break Swipe on the both of them eliminating Raichu, but not Manectric, who barely hung on & fainted at the end of the turn due to the burn. He then sent out Metagross & Ampharos. So, I sent in Mismagius, now that Gengar died, and one shot Metagross with Giest Beam. While Zygarde hit one break swipe before getting Dragon Pulsed to death. He then sent it Heatran and I was then left with a choice, Steelix or Sharpedo. Steelix couldn't get one shot by either of them due to its ability sturdy, but would die if it got targeted by both & it's to slow to out speed either of them, meaning it would likely only be able to attack once, at most, before fainting. While Sharpedo is not only resistant but also super effective to fire, just it's also weak Ampharos, who can one shot it. I chose Sharpedo as Sharpedo was definitely faster than Heatran & I knew Mismagius was faster than Ampharos, as I was able to take out Metagross, plus Ampharos had already taken damage to Break Swipe, so Mismagius could possibly finish it. I just didn't know if Sharpedo could out speed Ampharos, without priority, as Aqua Jet won't do alot of damage to an electric type Pokémon. Ampharos needed to go for me to win & I wasn't about to risk it living so I used Giest Beam & Night Slash on Ampharos, both hitting it and knocking it out before it could make move. Heatran then spammed nothing but Heat Waves while I hit my strongest moves on it. Geist Beam with Mismagius and the only water move Sharpedo currently knows, Aqua Jet. I nearly killed it before it healed with a Sitrus Berry, so I hit yet another Giest Beam & Aqua Jet combo but this thing was still standing, with it's health hust about in the red, before hitting another Heat Wave, killing Mismagius, and nearly killing Sharpedo. So I threw out Steelix & hit an Aqua Jet, hoping it would do enough to kill it, and it did, earning my 5th badge.