suffix, pre-noun adjectival
the most ... of all; the greatest ... in
A suffix-like expression attached to a noun denoting a group or domain, meaning 'the most outstanding ... in that group'. Used as a pre-noun adjectival, always followed by a noun. Common in phrases like チームきっての選手 (the team's best player).
彼は会社きっての営業マンだ。
He is the company's top salesman.
このレストランは街きっての名店です。
This restaurant is the most famous in town.