〜切る・〜切れない
do completely; can't (possibly) finish
Verb ます-stem + 切る / 切れる / 切れない
Sign up free to review this point on a spaced schedule.
切る after a ます-stem means doing something completely, to the very end: 一晩で本を読み切った, "I read the whole book in one night". 切る means "cut", so the image is of cutting it off at the end.
The potential negative, 切れない, means you can't finish it all, usually because there's too much: 一人では食べ切れない, "I can't eat all this on my own". 数え切れない, "countless", is a set phrase.
It also means "totally, utterly" with states: 疲れ切る, "be completely exhausted"; 分かり切ったこと, "something utterly obvious".
Compare 終わる, which only says an action ended. 切る says it was done fully, often with effort.
Examples
一晩で本を読み切った。
I read the whole book in a single night.
こんなにたくさん、一人では食べ切れない。
I can't eat this much on my own.
マラソンを最後まで走り切った。
I ran the whole marathon, right to the end.
夜空には数え切れないほど星があった。
There were more stars in the night sky than anyone could count.
疲れ切って、何もできない。
I'm completely exhausted and can't do anything.