Not counting gimmicks or abilities:
1. Lucario's Reversal at 1HP. Arguably Lycanroc Counter, depends on the opposing move.
2. Sirfetch'd's Fully-Powered Meteor Assault.
3. Infernape's Flare Blitz.
4. Sceptile's Solar Beam.
5. Dragonite's Draco Meteor.
6. Dracovish's Fishious Rend / Dragon Rush.
7. Pikachu's Thunderbolt / Charizard's Flamethrower / Lucario's Aura Sphere.
8. Charizard's Flamethrower / Lucario's Aura Sphere. / Pikachu's Thunderbolt.
9. Lucario's Aura Sphere / Pikachu's Thunderbolt / Charizard's Flamethrower.
10. Hypothetical Incineroar's Darkest Lariat.
Tier 1 - Recoil Moves / Sacrifice Moves / Situational Moves (Meteor Assault, Reversal, Flare Blitz, Counter). These moves are always depicted as the strongest moves that are used to either finish a battle or significantly weaken the opponent, even if the difference between both battlers is quite huge, case in point being Lucario's Reversal against Garchomp, Infernape's Flare Blitz against Electivire, and Sirfetch'd's Fully-Powered Meteor Assault against Garchomp and Mega Altaria.
In every single one of these cases, the moves were so powerful that the Pokemon by the end of their battles barely could move, Infernape couldn't join the fight against Tobias, Lucario could barely walk, and Sirfetch'd was completely out of energy. As for why Counter is here, it's one of the situational moves that can have as much power as a Bullet Punch, and as much power as a Fully-Powered Meteor Assault at the same time, so theoretically a high-end Counter would have twice as much power as these moves, but again, it's very situational.
Tier 2 - Charged Moves / All-Out Attacks (Solar Beam, Draco Meteor, Fishious Rend, Dragon Rush). These moves, while spammable to a degree, still are portrayed as having more firepower than the likes of Thunderbolt or Flamethrower, as they require some charging time, and if successful the results will be devastating to the point of being potential finishers, but not to the degree of the moves in Tier 1. Some might argue that Sceptile's Leaf Blade is superior as it finished Darkrai, but Solar Beam was consistently portrayed as the one move that it went for when finishing an opponent or firing all of its power, while Leaf Blade was the most effective option against an opponent of Darkrai's speed.
Some examples of usage to show how monstrous in power these moves can be include Sceptile's Solar Beam against Deoxys and Spenser's Claydol, Dragonite's Draco Meteor against Iris's Haxorus, Dracovish's Fishious Rend against Steven's Metagross, and Dracovish's Dragon Rush against Drasna's Noivern and Cynthia's Roserade.
Tier 3 - Spammable Powerful Moves (Thunderbolt / Flamethrower / Aura Sphere / Darkest Lariat). These moves can be used by the battlers whenever they want, at the maximum cost of some energy-draining which can be recovered through the course of the battle, they're usually the Pokemon's to-go move when starting a battle, and are more often than not present throughout members of the entire species, such as Pikachu's, Incineroar's, and Charizard's cases. Since these moves don't require some kind of colossal sacrifice on the Pokemon's part, or even charging time in order to use them to their full power, but still showcase enough power to put down powerful opponents.
Some examples of these move's powers are Pikachu's Thunderbolt throughout the entire anime, Charizard's Flamethrower tieing with Articuno's moves in power, as well as melting the field around him and Blastoise, Lucario's Aura Sphere finishing Volkner's Luxray and tieing with Cynthia's Garchomp Scale Shot, and a hypothetical Darkest Lariat from Incineroar would be supposedly as powerful as Kukui's Incineroar's Darkest Lariat, which was enough to tie with Pikachu's moves in power, and one-shot Kiawe's Marowak.
As for why I didn't use Greninja's Water Shuriken: I never saw that move in its base form as some kind of powerful move comparable to the ones stated above, it's definitely spammable, but it would most likely fall under a supposed Tier 4 of Spammable Moves, without the powerful part being considered, I always saw Greninja in his base form as more of a strategic fighter that while holds good firepower, is more adept to fighting like an actual ninja, by aiming for the opponent's weak points, avoiding as much damage as possible, and using his not powerful but fast attacks in creative ways, rather than being powerhouses that are mostly focused on destruction and firepower like Infernape or Charizard.
Ash-Greninja's powered Water Shuriken would definitely fall in the upper tiers though, with the base one being in Tier 3, the one used against Sawyer's Mega Sceptile in Tier 2, and the one used against Mega Charizard X's possibly even falling under Tier 1, as it was supposedly comparable in power to Blast Burn, which would easily be a Tier 1 move. And do note that I'm using these moves not considering their powers in the games themselves, but rather with how they are portrayed in the anime, which makes it significantly funnier to determine their powers.
