The greatest Ash was the one from season 1, he was a true champion, regardless of all his failures and mistakes that people seem to continue bringing up!
To make him greater, Ash should march all the way back to Johto, punch Misty straight in the face, where she will go flying into the nearest wall, hit it, fall down, bleed like crazy, Ash will go stomp stomp stomp stomp stomp stomp stomp stomp stomp stomp stomp stomp stomp stomp on her carcass, kick her like kick the can, then kick her like Pele, set fire to her orange hair, burn it all off, then drown her in the gym's water, until it turns Freddy vs Jason color red, and finally, piss on her while in da water, and pollute it with hard-stain oil!
As for Iris, frost her butt off into an ice block, then toss it down the deepest trench in Hoenn!
As for Serena, put a shock collar around her that zaps her anytime she goes out of bounds.
Then hunt down Tobias, drag his omnipotent butt back to the Lily of the Valley arena, tie up him and all of his Pokemon in his party, rechallenge him, defeat him unconditionally, and reclaim da trophy. He will be da champion!!!!!!!!
GREATEST ASH KETCHUM GOD EVER!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!