I wanted to wait until a few posts were made to post my own individual thoughts about Greninja. It’s no secret that I am vocal about keeping Greninja in the tier, for I like the presence it has in the metagame with it’s high speed, access to priority, and good offensive potential, keeping threats like Iron Moth, Latios, Ogerpon-Cornerstone, and Garchomp in line. It hasn’t felt overwhelming at all and there’s a lot of flaws that should be taken into account when handling Greninja. For one, Greninja is pretty weak coming off base 100 Special Attack, wanting Life Orb to have more flexibility while hitting hard. However, Life Orb absolutely kills its longevity and in tandem with hazards hinders Greninja from being a staying presence throughout a game that doesn’t always have chances to clean late game. The Specs set has been trending but falls into the issue of being prediction reliant as is the nature of all choice breakers with plenty of midgrounds into common attacks. I think Greninja is also generally Tera reliant on Tera Water or Stellar to pick up some KOes to even get the boost in the first place. Even with a boost Greninja isn’t unbeatable and we’ve got a lot of checks that can take Greninja on. I will use the set of Life Orb + Battle Bond with Hydro Pump/Surf, Dark Pulse, Ice Beam, and Water Shuriken for reference as it is the most common set. Sludge Wave and Grass Knot are viable options and do beat some of the listed counterplay but then other Pokemon become more reliable checks to Greninja as more impactful moves can be dropped. Before we get started, please be aware that these counterplay vary in reliability, but are all Pokémon considered counterplay nonetheless. Something like Ogerpon is more of a softcheck while Gastrodon is a hard counter, but both provide answers to it on varying teams.
In terms of counterplay (B or higher on the brand new VR) we have:
Offensive counterplay

resists all the moves and can easily pick off Greninja with priority Vacuum Wave.

also resists all of Greninja’s moves; Assault Vest which is very common shuts down Greninja entirely as it can’t do anything to hit it while the item lets it tank blows differently from how other sets would.

can take it out with Extreme Speed if low enough and can utilize Tera Normal to avoid being dropped by Water-type moves while picking off Greninja at a higher health.

easily KOes with first impression, not too much else to say.

same as Keldeo, can tank hits well and revenge kills Greninja easily apart from Tera Water Hydro Pump if Quaquaval ends up being chipped enough, but still a good check.

trades with and beats Greninja 1v1 thanks to its all around 100/100/100 bulk. Very solid tool to use on hyper offense

same as above, Galarian Moltres has good bulk that lets it check Greninja in an emergency for HO teams

Bulky enough to tank an Ice Beam from Greninja but can also use Embody Aspect and Tera to revenge kill Greninja with the Speed Boost

generally a really bulky trade Pokémon that acts as a backup / soft check on more BO / balance builds
Defensive counterplay

Roar phases Greninja out which can force it into more hazard damage, while Haze lets Empoleon handle it more easily in a 1v1 last mon scenario. It also neutralizes Battle Bond if already activated since it activates only once and possesses reliable recovery to take Greninja on.

specially defensive variants, which are solid due to its better ability to handle Zapdos and Tornadus-T, can check Greninja fairly well and possess the ability to heal itself with Pain Split

self explanatory I’m not writing this one out

rising option in the metagame for BO and balance teams that’s bulky enough to tank hits from Greninja and cripple it with Thunder Wave or knock it’s Life Orb or chip it more with Gigaton Hammer

very bulky on the specially defensive side, can phase out Greninja with Dragon Tail if Battle Bond has been activated, putting it out of commission for the game, or just outright KO it with Draco Meteor

Assault Vest sets destroy Greninja, self explanatory as well

has to watch itself around Dark Pulse but it can easily swap into Greninja’s other attacks and possesses reliable recovery to keep doing so. It also enables Pokémon like Hisuian Goodra, Hoopa-U, Tornadus-T, Tinkaton, and more to consistently check Greninja through Wish Support and slow pivoting

Assault Vest sets can stave off hits while threatening Greninja back. Icy Wind is a cool option to lower Greninja’s speed, forcing it to click the less consistent Water Shuriken option to get damage on you before being KOed
Reactive Tera- Lastly there’s reactive Tera options which are a completely valid way to handle Greninja. Slowking, Volcanion, Hydrapple, and Garganacl are just numerous options that can become solid checks to Greninja with tera in an emergency if the team really needs it.
All in all, this is a lot of counterplay to Greninja that I just mentioned. They are all easily able to fit on any archetype from HO to Balance and are also generally good Pokémon in the metagame. You don’t have to resort to dogshit to answer Greninja. Do get me wrong, Greninja is still a very powerful Pokémon and dangerous late game cleaner. It’s easily top 10 for me and if you’ve seen the VR you know it’s ranked A+. However, I just don’t see a world where it’s too overbearing with all the answers we have. I don’t personally see a need to even proceed with tiering action on it nor have it planned in the future. With UUPL coming soon and masters ongoing, we can utilize tournament replays to examine Greninja’s effect on the tier, but as of now I don’t see Greninja as an unbalanced threat and I think it should stay in the metagame.
Since I don’t want to double post, this also serves as an announcement that we will begin to reach a verdict in the coming days on Greninja’s presence in the tier. If you’ve got any last words, please get them in before the thread is closed. It will be locked in about 3 days. We are looking forward to hearing any final thoughts!