expression
to the very end; thoroughly; to the hilt
Emphasizes doing something completely, without holding back, or until the last possible moment. Often used with verbs like やる, 戦う, 話し合う, 楽しむ.
彼はとことんまで戦う覚悟だ。
He is prepared to fight to the bitter end.
この問題はとことんまで話し合おう。
Let's discuss this issue thoroughly.