James set a Miami Heat record with a 23-point first quarter, then set a personal best by hitting his first 11 shots of the game. James finished the half with 29 points, helping the Heat to a 55-45 lead at the break.
"Anybody that questions my competitiveness, they must be looking at the game the wrong way," James told TNT in a televised interview at halftime.
James remains bothered by something Magic President Otis Smith said last summer. Referring to James' decision to join the Heat, Smith said, "I thought he was, I guess, more of a competitor."
James has referenced that line often since July, including earlier this week.
James was 9 for 9 from the field in the opening period Thursday night, mostly on midrange jumpers, scoring all but seven of Miami's points in the first 12 minutes. He also made five of six free-throw attempts.
Alonzo Mourning previously held the Heat's first-quarter scoring record, scoring 21 against Washington on March 29, 1996.
James' 11 straight makes to start the game was the longest stretch for any point of a game in his career, according to STATS LLC. He made his first 10 shots against Chicago on April 11, 2008.