Team Rocket: This one is hard to pin down, because they appear in every season and region instead of just Kanto. Personally I think that the climax is BW097. A lot of important stuff happens in this episode. Giovanni almost goes so nuts he dies, Team Rocket controls the Genies, and Meloetta is imprisoned. Ash meets Giovanni in this episode and others.
Team Magma/Aqua: AG097 is where Groudon and Kyogre are awakened, and the power of the evil teams is at its strongest.
Team Galactic is what you said
Team Plasma: BW121 and BW122 are the climax of Team Plasma, where Ghetsis summons and then takes control of Reshiram, Jesse and James help the "twerps" and Looker eventually arrests Ghetsis.
Team Flare: Honestly, you could arguably say the entirety of S19 Pokemon XYZ was the climax of Team Flare. XY136 though, is where Squishy turns into 100% Zygarde and Lysandre disappears, which leads to the defeat of Team Flare
Team Skull and the Aether Foundation: Well, there isn't one. Team Skull isn't a major part of the story, they're just ruffians and rebels who get in the way sometimes. And the Aether Foundation isn't really bad in the anime. The main villains of the SM anime are the Ultra Beasts. The climax of the SM anime arc is SM090 where Ash and everyone else fights Ultra Necrozma.
Macro Cosmos and Team Yell: JN045 is the climax of Macro Cosmos, with Ash and Goh defeating Eternatus with the help of Zacian and Zamazenta, causing Rose and Oleana to go into Hiding. Team Yell however barely have a role in the anime, having only a single Antagonizing part in JN099 where they sent Ash and Goh to Spikemuth, Hoping to make them late for their match with Marnie in Wyndon.
