The connecting record
shownNaruto · ch. 142–144
Itachi Uchiha beat Kakashi Hatake in Naruto.
A genjutsu result: Tsukuyomi leaves Kakashi unconscious, and he is still bedridden days later.
What each of them is ranked on
The winner · Itachi Uchiha · rank 8
classic · shippuden
Joint holder of the largest figure the books ever issued, and he does not survive to meet anything in the tier above him. The record supports the number as far as it goes — a complete Susanoo, a genjutsu nobody counters honestly, and a fight against his own brother that he loses on purpose while dying of an illness. What it cannot do is compare him to opponents who arrived after the book went to print.
statedNaruto Databook 3 · 2008
Rated 35.5 of a possible 40, the joint highest total published.
shownNaruto · Sasuke and Itachi arc
Fights Sasuke using Susanoo and dies at the end of the encounter. — 2008
Beaten · Kakashi Hatake · rank 14
The Sixth Hokage — classic
The rank ladder's other broken end. He clears genin as a small child and is a jonin while his eventual students are toddlers, which makes him the fastest promotion in the setting and the exact mirror of the protagonist who never got one at all. Two people, one system, opposite failures. He is also in the room for the Kaguya fight, which very few of the graded names above him can say.
statedNaruto · Kakashi Gaiden
Holds jonin rank as a child, years ahead of his contemporaries. — 2005
shownNaruto · Kaguya arc
Fights Kaguya alongside Naruto, Sasuke and Sakura. — 2014
What this does not settle
One fight in one work. It is the only result the record gives between these two, and it is evidence about that meeting and nothing wider — not a general matchup, not a rematch, and not a ranking of its own.
The ladder above it is argued from everything either of them has been shown doing; this page is argued from one citation.
Where the two disagree, the disagreement is the point, and it stays visible rather than being resolved by whichever of them happens to be on this page.