～切る
do completely / to the end
～切る（～きる）attaches to the ます-stem of a verb and means the action is carried through all the way to completion: 使い切る “use up”, 読み切る “read to the end”. With states it means “utterly”, as in 疲れ切る “be completely exhausted”.
1. Completing the action entirely
Use ～切る when every last bit of the action gets done.
ラーメンを最後まで食べきった。
“I finished the ramen down to the last bite.”
- ラーメン = ramen
- を = object marker
- 最後まで（さいごまで）= to the very end
- 食べきった（たべきった）= ate it all up
2. ～切れない: can't do it fully
The negative potential ～切れない says the action is too big to ever be completed.
空には数え切れないほどの星があった。
“There were countless stars in the sky.”
- 空（そら）= sky
- には = location + topic marker
- 数え切れない（かぞえきれない）= cannot count them all
- ほど = to the extent that
- 星（ほし）= stars
- が = subject marker
- あった = there were
How to form it
Verb ます-stem + 切る（negative potential: ます-stem + 切れない）
- 使う（つかう）= to use → 使い切る（つかいきる）= use up completely
- 食べる（たべる）= to eat → 食べ切る（たべきる）= eat it all
- 数える（かぞえる）= to count → 数え切れない（かぞえきれない）= can't count them all
Key idea
～切る pushes an action to 100 percent: done completely, with nothing left over. Flip it to ～切れない and you get “too much to ever finish”.
Other N2 grammar
Updated .