Yanmega is one of my favourite mons of all time and i absolutely loved using it last gen, since it helped a lot in the Fighting and Dragon matchup. This gen is not as good as last gen but it can still be a good late game cleaner for Bug teams thanks to its ability Speed Boost. First off, we start with the imposted core: Yanmega+Galvantula.
Yanmega is run with Protect and Modest to maximize its sweeping power with STAB moves like Bug Buzz and Air Slash, the later one helping a lot against Fighting as i've said before. HP Ice is a coverage move i run over Giga Drain because it gives the team more chances to get rid of Stealth Rock in the Dragon matchup (Armaldo can't repeatedly spin in front of TankChomp due to Rough Skin+Rocky Helmet). Something important to note is that Yanmega can outspeed and OHKO with Bug Buzz Choice Scarf Latios at +2, which is important for a type that struggles with Choice Scarf Latios with HP Fire. The other mon of the core is
Galvantula, which is Bug's best Sticky Web setter, ensuring the team gets a source of speed control thanks to Focus Sash. Galvantula is also really useful in the Water matchup and against bulky Water-types like Toxapex and Mantine, since it learns Thunder whose accuracy is boosted by Compound Eyes. Energy Ball is coverage to hit Water-types that are immune to Thunder such as Swampert, Gastrodon, Seismitoad and Lanturn, and HP Ice gives the team another way to ease the Dragon matchup and prevent Stealth Rock. The next thing a Bug team needs is a spinner, and
Armaldo it's the best Bug has access to. Rapid Spin is mandatory to get rid of entry hazards, and Rock Blast is the STAB move of choice over Stone Edge to be able to deal with SubToxic Zapdos, which otherwise this team would be very weak to. Knock Off is an utility move that lets Armaldo remove Rocky Helmet from bulky mons like Skarmory to be able to spin repeatedly in front of them, and Stealth Rock helps its teammates to get KOs. Full HP and SpD lets Armaldo take one Fire Blast from Mega Charizard Y under the sun at full health. For the mega slot i chose Mega Scizor, since the other slots were for two things the team needed: Volcarona+Heracross.This meant i couldn't go for Mega Heracross, and Mega Pinsir+Yanmega would have been very redundant.
Mega Scizor gives the team a way to deal with massive threats like Nihilego and Terrakion, as well as acting as a cleaner with Sword Dance boosts combined with both STAB moves Bullet Punch and Bug Bite, and coverage for Steel-types in Superpower. Opting for Mega Scizor for the mega slot left the team almost unable to break Toxapex, since even Galvantula can't OHKO it with Thunder. I decided to run Psychium Z
Volcarona to solve that problem, with Fire Blast as the STAB move of choice and HP Ground to hit Heatran, which would otherwise wall Volcarona. Volcarona is a 'must' in Bug teams, providing a wincon against Steel teams. For the last slot i opted for Choice Scarf
Heracross over Buzzwole (which was my other option) because it learns two powerful STAB moves: Close Combat and Megahorn. Heracross provides the team with a source of speed control outside webs. Stone Edge is to mainly check Mega Charizard Y and help in the Fire matchup, and Pursuit deals a considerable amount of damage to Victini after using V-create when it switches out.