~切る
Carry an action completely through to the end
You’ll be able to emphasize full completion, exhaustion, or doing something without leaving any remainder.

険しい山道を最後までみんなで登り切った。
kewashii yamamichi o saigo made minna de noborikitta.
What do you think this sentence means?
We hiked the steep mountain trail all the way to the end together.
Carry an action through to the very end
Attach 切る to the verb stem to express carrying an action all the way through to completion without giving up ("do all the way through", "finish completely").
大きなペットボトルの水を飲み切った。
ookina petto botoru no mizu o nomikitta.
I drank the whole big bottle of water.
一日中働いて、疲れ切っている。
ichinichijuu hataraite, tsukarekitte iru.
I worked all day and I am completely exhausted.
Attach 切る to the masu-stem
Attach 切る directly to the verb stem (masu-stem). It conjugates as a godan verb (切ります, 切った, 切らない). Common compounds include 走り切る, 使い切る, 読み切る, and 疲れ切る (exhausted).
今月のお小遣いを給料日前に使い切ってしまった。
kongetsu no okozukai o kyuuryoubi mae ni tsukaikitte shimatta.
I spent all of this month's allowance completely before payday.
~終わる vs ~切る
~終わる simply says an action is finished. ~切る stresses doing it all the way through, with nothing left over or with real effort.
~終わる, finish doing
長い小説を読み終わった。
nagai shousetsu o yomiowatta.
I finished reading the long novel.
Just says it is done.
~切る, do all the way through
長い小説を読み切った。
nagai shousetsu o yomikitta.
I read the long novel all the way through.
Stresses getting through the whole thing.
寒い中で一時間もバスを待っていたので、体が冷え切ってしまった。
samui naka de ichijikan mo basu o matte ita node, karada ga hiekitte shimatta.
I waited for the bus in the cold for a whole hour, so I got chilled to the bone.
祖父は八十歳で、十キロの海を泳ぎ切った。
sofu wa hachijussai de, jukkiro no umi o oyogikitta.
At the age of eighty, my grandfather swam ten kilometers of open sea all the way through.
三か月も雨が降らず、畑の土は乾き切っている。
sankagetsu mo ame ga furazu, hatake no tsuchi wa kawakikitte iru.
It hasn’t rained for three months, and the soil in the fields is completely dry.
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