For Double, I had originally planned to win 70 battles just like in Single. But since I had 3 different teams and I wanted to make things fair between them, I decided to win 30 battles with each team, which would give me a total of 90 wins.
Team 1:
The team I used for the first 30 battles was
this team by
DaWoblefet. It consists of Zacian, Eternatus, Gyarados and Rotom-Heat.
This team was very easy and straightforward to use. Zacian and Eternatus are extremely powerful leads, they destroyed most opposing teams on their own. However, I found Eternatus' Dynamax Cannon surprisingly underwhelming here, it didn't always OHKO opponents whenever I used it, which was very unexpected. I had to use Gyarados and Rotom a few times here but not that often. I Dynamaxed Gyarados a few times when I used it, but not always. There weren't any close battles along the way, I am pretty sure I had at least 3 Pokémon still alive at the end of every battle. In the very worst case scenario, Zacian or Eternatus had fainted while the other one was heavily damaged. But it was never any real danger in those situations. I remember that I met an Imposter Ditto along the way here as well, and like when I met the previous one in Single, it copied Zacian. But this time, I defeated it easily by ganging up on it in order to take it out before it could cause any major issues.
I don't have much else to say here. This team is really good and the leads alone are enough to beat most opponents. I can definitely recommend this team for anyone who wants to reach Max Rank and Master Ball Tier in Double, and I can see this team work for getting high streaks as well. But again, there's a chance I'm wrong since I only did 30 battles with it.
Team 2:
The team I used for the next 30 battles was
this team by
insanemaniac. It consists of Weavile, Gyarados, Zacian and Eternatus.
This team is similar to the previous one, with 3 out of 4 Pokémon being the same. But at the same time, there are several important differences. It had to be played differently compared to the previous team since the legendaries were the backups and not the leads this time around. Some of the movesets also differed from the ones I had used before. My main strategy with this team was to use Fake Out with Weavile and Dragon Dance with Gyarados on turn 1, then Dynamax Gyarados and sweep, gaining Moxie boosts as it defeated opponents. Weavile could support once more with Fling if necessary. Gyarados often became unstoppable after getting enough Attack boosts from Moxie combined with the Speed boosts and Rain from the Max moves. I let Weavile do what it could before it fainted, or switched it out if I felt that it wasn't worth letting it faint. Zacian or Eternatus could take over after Weavile or Gyarados had fainted, they were powerful sweepers here as well. I occasionally switched out Gyarados as well, but it was rare. One situation I can remember was when I was up against two Electric-type leads.
I guess there are some alternatives for the team's movesets. insanemaniac has some ideas for changes in the original post, and I agree with several of them. Weavile could definitely benefit from having a stronger Ice-type move, Ice Punch could go over either Throat Chop or Ice Shard. But this still worked, Throat Chop was useful as a strong Dark-type move and for other random stuff, I once used it to prevent a Liepard from using Hyper Voice and felt happy afterwards. Ice Shard could also be good at times, having a move with increased priority is never bad. I guess another alternative could be to remove Fling as well as change the King's Rock for a Focus Sash since I found that one turn of flinching was usually enough for this team to win. But this worked, so I'm not really sure.
I would not remove Dragon Dance on Gyarados since I found that setting up once before Dynamaxing was extremely useful. Though I suppose Earthquake could also be used over Dragon Dance if you don't want to set up, this could make it easier against Electric-types. Just an idea.
Zacian's moveset could be changed though, I missed Play Rough and Close Combat since the two previous Zacian I used had those moves. Those two moves could be used over Psychic Fangs and Sacred Sword. I'm not sure if I ever used Psychic Fangs. While it has better accuracy than Play Rough, it doesn't get a STAB bonus. Close Combat is much stronger than Sacred Sword while Sacred Sword can ignore Defense and Evasion boosts, so it has a extra purpose over Close Combat. Though I never got into any situations where that would have made a difference. I did not miss Swords Dance since it is harder to find opportunities to set it up in Double, and Crunch was very useful for coverage.
Eternatus could also use some changes. The only two moves I ever used with it was Dynamax Cannon (which once again was a bit underwhelming, I remember that it failed to OHKO a Jolteon once) and Flamethrower. Sludge Bomb is standard and should definitely stay. I would also keep Flamethrower for sure, but I guess Flash Cannon could be changed. Though I'm not sure what could be used over it. Maybe something like Eternabeam or Draco Meteor since the previous 2 Eternatus I used had these moves, but I never used them on these teams, so I don't really know. I guess there's also Shadow Ball, but I don't think it offers any significant coverage. It feels like 3 moves are enough for Eternatus in most if not all situations.
With this team, I had one really close battle along the way. It was against a Hiker who had a team consisting of Mudsdale, Froslass, Quagsire and Rhyperior. I misplayed and lost both Weavile and Gyarados on turn 1. I completely forgot that Mudsdale could have Inner Focus and I did not expect Froslass to use Thunderbolt (which was something I definitely should have expected). After that, I sent out Zacian and Eternatus. They managed to sweep the entire opposing team, but it was close. Zacian also got heavily damaged along the way.
There was also another battle which is worth mentioning, it was my last battle against Leon with this team. It wasn't very close and I don't remember the exact details, but I only had two members of my team left near the end of the battle, he managed to defeat the first two. But at that point he only had his Aegislash left against my two team members, giving me an easy victory.
Other than that, I had at least 3 Pokémon alive at the end of every battle. And I believe the only one that ever fainted during those battles was Weavile.
On the whole, this was another good team. It was a bit different compared to the previous one but I can definitely recommend it to anyone who wants to reach Max Rank and Master Ball Tier. I can see it work for getting long streaks too, I'm not surprised by insanemaniac's streak and I can definitely see it working for getting even longer streaks.
Lastly, I just want to say this to insanemaniac. I'm sorry, but I didn't like the nickname for your Eternatus! The nicknames for the others were fine. I just prefer more serious nicknames for Pokémon. Still a great team though!
Team 3:
The team I used for the last 30 battles was
this team by
Adamant Zoroark. It consists of Dracovish, Whimsicott, Galarian Weezing and Gyarados.
I decided to save the team with no legendaries for last in order to make it more challenging for myself.
This was another great team. The main strategy was to set up Tailwind with Whimsicott on turn 1, then destroy everything with Dracovish's Fishious Rend. Whimsicott and the others did of course help, but Dracovish did most of the job here. Fishious Rend was the only move I ever used with it, never clicked the others. The move in question defeated a vast majority of opponents, only a few survived. I had to switch out Dracovish a few times in some situations, such as where its Attack had been lowered or against two bulky Grass-type leads, but those situations were rare. I usually put priority on defeating Pokémon that could defeat Dracovish since I wanted to keep it alive in the battle for as long as possible.
Whimsicott usually set up Tailwind and then attacked, though I had it use Taunt as well on a few occasions. It was usually the first to faint on the team, sometimes I switched it out if that felt like the better alternative or if I wanted to let it stay alive for a potential comeback later in the battle. Gyarados was the third most used Pokémon, I usually Dynamaxed it right away whenever it got out on the battlefield. It could support the team with Rain and Grassy Terrain, Dracovish benefitted greatly from the Rain. The Wacan Berry let it survive an Electric move from a Manectric once, so that was good. Weezing was the one I used the least, it was sent out whenever I needed to get rid of an annoying Ability on the opposing side, or when I needed it for offensive coverage or defensive support.
I had no super close battles with this team, the closest one happened when I got down to only having 2 Pokémon left because an opposing Crustle unexpectedly activated its Quick Claw. But that wasn't a close or scary battle since I was about to win anyway. Other than that, I always had at least 3 Pokémon still alive at the end of every battle.
There was also another battle which wasn't close, but worth mentioning anyway. I met an opposing trainer who was also leading with a Dracovish and I decided to try to defeat it with Fishious Rend... only to find out that it had Water Absorb. I didn't know that it could have Water Absorb as an Ability. I have to shamefully admit that I don't know the Abilities of all the Gen 8 Pokémon, and there are some from the previous generations that I'm not 100% sure about either (and some that I have forgotten about, such as Mudsdale with Inner Focus which I mentioned earlier). But I guess there are some things you have to learn the hard way. The rest of this battle wasn't close, but it got very scary in the beginning because of the mistake I made there.
Lastly, there's one more thing that happened with this team. I met another regular trainer who Dynamaxed a Pokémon. This time, I wrote down who it was: League Staff Lazlo, who Dynamaxed his Inteleon on turn 1. The battle itself was no problem, just an easy victory as usual, but I thought I'd mention that it happened.
That's it for this team. To summarize, this team was really good and quite easy to use too. Dracovish destroyed most opponents extremely hard. I can recommend this team to anyone who wants to reach Max Rank and Master Ball Tier. I can see it work to get long streaks too... guess that's the fourth time I'm saying that. But yeah, all of the teams I used for the Tower were really good. Looking back, I find it funny how all four teams featured a Gyarados. I guess that (Dynamax) Gyarados is just a really good Pokémon for the Tower, both in Single and Double.
In the end, I won 30 battles with each team, just as planned. I didn't lose any battles along the way, which gives me ongoing streak of 90.