tenacity; persistence; obsession; implacability
彼の執念が長年の研究を実らせた。
His tenacity bore fruit in years of research.
犯人逮捕への執念が刑事を突き動かした。
The obsession with catching the criminal drove the detective.
執念深い性格が時に周囲を困惑させる。
His persistent nature sometimes bewilders those around him.