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I just wanted an ice type, and this one seemed fitting due to the immense wall breaker potential. I also like it for the sheer fact that it's an ice cream.
Hey there and welcome in Underused aka the best Smogon's tier. I understand your build process but I'm not gonna lie to you, Vespiqueen is a really really bad Pokemon in the tier. Too weak, too slow, too weak to Stealth Rocks for what it brings to a team.
If you want to build around a Bug Type in Underused, there is basically 2 possible pick ; Scizor or Beedrill-Mega. I'm gonna try to help you with both of them.
• I'm gonna keep your idea of Hippowdon + Tentacruel because it's a really good Hazard Core in Underused. Both of them can support Scizor pretty well. Hippowdon can weaken Steel types thanks to Earthquake and set Stealh Rocks with is always a good thing. On the other hand Tentacruel can use Rapid Spin which is good for Scizor because it's a Pivot which does a ton of back and forth during a match with U-Turn. Tentacruel can also handle most of Fire Types which are really dangerous for Scizor.
• Now, the team need something which can handle Hydreigon and Latias because they're deadly vs the current team. There is 2 good option to deal with them. The first one is to play Sylveon + Hydreigon. Sylveon is one of the best Pokemon to deal with Hydreigon and can handle most of Latias variant. Choice Scarf Hydreigon brings some Speed to your team while also being able to Revenge Kill non-Choice Scarf Hydreigon / Latias (or Choice Scarf if they're locked on Dark Pulse or Psychic). On the other hand, you can opt for Togekiss and Choice Scarf Krookodile. Like Sylveon, Togekiss is able to deal with most of Hydreigon variant while Scarf Krookodile can trap Latias thanks to Pursuit or just Knock Off.
• At that point, Sylveon's variant struggles vs Water Types so Manectric-Mega or Zeraora is a good pick. It also brings to the team a Pokemon that can check Flying Types. On the other hand, Krookodile's team is too weak to Ice Types and especially Mamoswine which pressures 4/5 of the team. With that in mind, I decided to change Hippowdon and put Bronzong instead. Since you want an Ice Type Pokemon, I decided to add SubRoost Kyurem which enjoys Tentacruel's Toxic Spikes (you can also opt for Sub / Protect Suicune).
• Like Scizor, I decided to paired Beedrill-Mega with Hippowdon because it can check some Beedrill-Mega's threats like Scizor or Aerodactyl-Mega. I opted for an EV Spread which allows Hippowdon to be only 3HKO by Aerodactyl-Mega's Aqua Tail. Because Beedrill-Mega likes Momentum, I opted for Rotom-Heat instead of Tentacruel because Volt-Switch paired well with U-Turn. Rotom-Heat can also check Flying Types.
• Because the teams needs something to handle Dragon Types and especially Hydreigon, I decided to add Primarina. Choice Specs paired really well with Volt-Turn Core but Defensive Primarina can works as well.
• Because Momentum is Momentum. I opted for Choice Scarf Hydreigon and Swords Dance U-Turn Scizor. Like Rotom-Heat, they help Beedrill-Mega with U-Turn and both of them can check Latias which can Revenge Kill Beedrill-Mega if it holds Choice Scarf.
