Kukui literally functions as the champion of Alola though prior to Ash, just not having the title because of there not being a league, but he's shown as the top trainer of Alola, the strongest and most famous, which is what a Champion is. Heck the way he's portrayed in the anime is just like how other Champions were, down to the point of him giving Ash a severe one sided beat up in the episode litten evolved, with even its evolution not being able to lay a scratch on Kukui's Incineroar
If this were the case, then what about Drake? He was in the exact same place as Kukui, however Ash defeating him did not make him a Regional Champion tier.
Lol are you kidding me? Ash used a rookie basic Pokemon against Kukui. We've seen other Champions absolutely destroy and wreck fully evolved veteran experienced pokemon.
We see Cynthia absolutely destroy Paul's Torterra which would be relative to some of Ash's experienced Aces. We see Steven Effortlessly hold his own against Alain's MCX (Which later goes on to be the first pokemon that actually beats an E4).
Most of your argument is based off your headcanon.
Tell me with a straight face Iris, Drasna, Raihan, Wallace were even shown close to a challenge as Kukui was. He's literally the end game boss, the Leon of SM.
This is a dumb argument. Being the Last battle does not = Regional Champion tier.
In Johto this was Harrison, in Hoenn this was Tyson, in Sinnoh this was mostly Paul (Tobias was more of a plot device inserted to stop Ash from winning the league), In Unova (Trying to forget about this), in Kalos this was Alain.
Ash was in fact shown to be much inferior to elite four members/Regional Champions until Journey's. Claiming their fights seem less intensive is not an argument to rate Kukui above.
Ash is just scaled to be that much stronger as his current end boss is the "Established" Strongest Trainer in the world.
At this point it feels you are avoiding and downplaying the narrative just to push your own powerscaling, when the anime rejected and refuted it, and clearly gave his status more preference and importance in regards to Alola's champion then any other feat.
Most of your power scaling regarding Kukui is based on your headcanon. Ash is always the underdog in almost all of his main battles. The simple fact is, we do not see Kukui actually defeat an Elite four member or Regional Champion on Screen.
Alain on the other hand, was the first trainer we see take down an Elite four Member in an actual battle and then go on to enter the PWC and reach the Master Class.
