Luka Doncic and James Harden were tied for the most games with 15+ assists, 35+ points and 15+ rebounds, with 1 game.

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who has the most career games with 35 points, 15 assists and 15 rebounds
Interpreted as:
Who has the most career regular-season games with 35 or more points, 15 or more assists and 15 or more rebounds?
Luka DoncicLuka Doncic136151637.536.
James HardenJames Harden153171642.
StatMuse has game-level data for assists and rebounds going back to the 1982-83 season.