きる

1. 1To carry an action through to completion, leaving nothing unfinished.Ex. 1
2. 2To finish covering a whole distance or amount, all the way to the end.Ex. 2
3. 3With state verbs, to be in that state completely or extremely (e.g., 疲れきる, 困りきる).

Neutral in register and common in both speech and writing, it often conveys a sense of accomplishment after effort (finishing homework, running a full marathon, using something up). Compared with 終わる, which simply marks that an action ends, きる stresses that the whole task or amount is fully covered. Compared with 抜く, it focuses on completeness rather than perseverance through difficulty.

• 切れないN3「切れない」is the negative of the potential form 「きれる」, and is used when the amount or degree makes it impossible to finish or fully do something, as in 「待ちきれない」 ('can't wait any longer'). 「きる」, by contrast, means doing something completely or a state reaching its extreme, so the two are not interchangeable.
• 抜くN2「抜く」places more weight on the hardship of the process and the willpower required, or on doing something repeatedly and deeply to the very end (「考え抜く」), and it sounds unnatural with actions that are easy to do (「ご飯を食べ抜く」). When it comes to persevering through something difficult to the end, it can be used interchangeably with 「きる」.
• てしまう / ちゃうN4「てしまう」attaches to the て-form, with the colloquial forms 「ちゃう／じゃう」. When it means 'finish doing,' it is close to 「きる」 but does not emphasize seeing something through, instead reflecting the speaker's relief or regret; it can also express something irreversible or unintentional, and it has no usage for a state reaching its extreme.
• 終わるN4「終わる」also attaches to the ます-form, but it only objectively states that an ongoing action reaches its endpoint, without emphasizing thoroughness or perseverance, and it has no usage for a state reaching its extreme like 「疲れきる」. It is often used together with 「まで」 or 「たら」 to mark a time limit.
• 続けるN4「続ける」also attaches to the ます-form, but it focuses on the action continuing without interruption, regardless of whether it gets finished, while 「きる」emphasizes reaching the end with nothing left over. For example, 「走り続ける」means simply running on and on, while 「走りきる」means running the full course, so the two cannot be swapped.

切れない is the negative potential form ('cannot finish / too much to'), 抜く stresses persevering to the end despite hardship, and てしまう (attached to the て形) marks completion often with regret. 終わる simply marks the end of an action without implying totality, while 続ける means to keep doing something rather than complete it.