one second that could change the entire timeline of naruto if it didnt happen.
add any moments that you can think of that, had the not happened would entirely change the timeline of naruto.
mine is when lee blinks when fighting gaara.
here is why. if lee hadnt blinked when fighting gaara, gaara wouldnt have had a chance ti swap himself for a sand shell and lee would have succesfully lotused him, thus making gaara lose the fight. because of this, sasuke would never have learned chidori as he would not have to fight gaara. in addition, he would not know about lee's 5 gates, and lee would probably overpower sasuke.
also, due to gaara not being in the finals, he had plenty of time to activate shukaku mode and the leaf would almost certainly have been crushed.
so, the leaf was saved thanks to the sacrifice of lee's right arm and leg.