1. Since XY Started, Pikachu first Lost against Viola in his first gym battle with her.
2. Ash’s Pikachu then lost to Clement‘s Luxray after defeating his bunnelby. And it is important to note that Bunnelby was a Pokemon Clement recently caught and it was no where as experienced as Pikachu.
3. Tapukoko and Kukui is NO WHERE close to elite four tier. Firstly, Kukui’s Strongest Pokemon, i.e his ace was defeated by Ash’s torracat. Are you saying Ash’s torracat is stronger than his Charizard/ Infernape with much greater feats who are no where close to elite four tier?
4. Defeating a Legendary Pokemon is nothing new. Ash has defeated Legendary Pokemon much before this. His Pikachu has defeated a Regice and tied with a latios much before this. If anything, I could easily argue Brandon is a much more experienced and stronger trainer than Kukui and Pikachu‘s victory against Regice is much > than his victory against Kukui and Tapu Koko.
6. Another Interesting point that is left out. You consider grappoloct defeating the Pikachu that defeated Tapu Koko a great feat? Understood. Now if you go back to Sinnoh, the same Pikachu that defeated a Regice, ties with Paul’s elekid. So wouldn’t Paul’s elekid is on the same level as Brandon’s regice? And we all saw Paul’s and Brandon’s battle.
A pokemon can only be considered elite four tier if it actually puts up a fight against an established elite four tier pokemon. You assuming Kukui’s tapu koko is elite four tier is simply head canon and not an established fact. Alain’s Charizard on the other hand, is established elite four tier and ash greninja putting up a fairy even fight against it is something you can recognize as elite four tier.
6. Now let us go back to Pokemon Journeys. Ash’s Pikachu didn’t dominate the fight against Raichu used by Pisces. It technically didn’t even dominate the fight against the trainer with the Mightyena in the battle frontier tournament. On top of that, Pikachu took a lot of damage against the random kid with the Meganium. So are you saying all these guys are almost strong enough to hold their own against the Elite four because of their respective battles with Pikachu?
Ash’s Pikachu is the most inconsistent Pokemon in terms of strength out of all of his team. This is because Pikachu’s strength is often reset to sync with the rest of his team.
7. Oh and with regard to your argument while mentioning Paul’s battle against Cynthia. You conveniently left out how an attack from Paul’s torterra was strong enough to drop Garchomp to the ground. Pikachu on the other hand was only able to cause any form of damage to Leon’s Charizard when it dynamaxed Before Charizard was able to gigantamax.
Plus, that isn’t something you call as “Holding it’s own in battle”. Holding it’s own in battle would be Ash Greninja vs Charizard X. Ash’s Pikachu was simply dominated in his fight against Leon.
Pikachu is inconsistent in terms of strength period.
1-2 They are Gym leader's ace pokemon, so that's not as bad as the loss against Trip's Snivy. That's what I mean with Pikachu not having been
that inconsistent anymore after XY. He's still inconsistent, of course, but not as much as before.
3- Again, I don't agree. Tapu Koko is a Legendary pokemon, they're always portrayed as having superior strength in the anime. Now if you add a Z-move on top of that? There's no way that amount of power can't compete with the power of an attack from an E4 pokemon.
If you put Ash's Pikachu Z-Move that overpowered Tapu Koko's Z-Move, against Malva's Houndoom, the result would be the same. A Houndoom can't be stronger than a Z-Move powered Legendary pokemon, no matter if it's from an E4.
And before you say that's speculation, everything you or me or anyone here says it's speculation, since that's what this is about.
I also don't agree that Ash's Charizard is nowhere close to E4 tier.
And Kukui's Incineroar was taken down by a colective effort, he fought Torracat, Lycanroc and Melmetal before facing Torracat again and only then going down to his Z-Move. Incineroar was unbeaten as Royal Mask's partner for who knows how long, he even defeated TR's Mega Aggron easily. So that does put Kukui's Incineroar at least at low E4 level.
I do agree that Pikachu's power is inconsistent so we can't really measure Bea in comparison to it.
But I don't agree that he struggled against Mightyena or Meganium. The Meganium trainer even said that no pokemon had ever withstood Meganium's Solar Beam before, and Pikachu took it point blank and then defeated Meganium with Iron tail.
That's clearly showing Pikachu is not an ordinary pokemon, if it's the first one to survive Meganium's strongest attack.
About Torterra vs Garchomp, no, Frenzy Plant did not drop Garchomp to the ground. Garchomp took the attack standing because he was recharging from Giga Impact, but he was not damaged at all.
Greninja vs Zard is not holding it's own, it's "almost winning". I take "Holding it's own" as not being completly outclassed and being able to put somewhat of a fight, which Pikachu did, imo.
Lastly, I think you're way overestimating the E4 power. If this series goes the way we expect it to go, Ash will be battling and defeating E4 level trainers by the end of this series, likely even using his current team, which are his less experienced ones.
The days were the E4 was portrayed as untouchable are long gone.