Shaq says a slap from his stepfather during a high school game set off his determination to dominate

After Shaquille O'Neal's stepfather slapped him for playing too softly in a high school game, the big man became determined to dunk every time down.

• Shaquille O'Neal says in HBO's "Shaq" that his stepfather slapped him in the face during a high school game for playing too softly.
• O'Neal says the slap encouraged him to dominate from then on.
• O'Neal's desire to dominate opponents and make a name for himself became a through-line in his career and in the docuseries.

A slap in the face from his stepfather set off something inside Shaquille O'Neal.

In HBO's four-part docuseries "Shaq," O'Neal describes his development on the basketball court. Despite being tall early in life, he was uncoordinated and out of shape. He slowly developed over his high school years, but was not yet the dominant force that would rule the NBA for a decade.

In his senior year of high school, O'Neal became enamored by Magic Johnson and wished to emulate the 6-foot-8 point forward.

During a high school game, O'Neal said he crossed over a defender on a fastbreak and went up for a smooth finger roll. He missed.

That's when his stepfather, a sergeant in the military, approached O'Neal and asked what he was doing. When O'Neal said he was working on his Magic Johnson-style game, his stepfather slapped him.

"'Fuck that,'" O'Neal remembers his stepfather saying. "'Be Shaquille O'Neal. Dunk it every fucking time.'

"The boys knew what happened. They knew Serg done touched me up ... When I dunked, I was so fucking mad I wanted to break the rim off. For him."

From that point on, O'Neal began to physically dominate opponents. O'Neal averaged 31 points, 22 rebounds, and 6 assists per game his senior year as his team won the Texas state championship.

He went on to average 21.6 points and 13.5 rebounds per game across three seasons at LSU before becoming a 15-time All-Star, one-time MVP, and Naismith Hall of Famer.

That desire to dominate became a constant theme in O'Neal's career. As he says in the documentary, if he couldn't be definitively called the best big man of all-time, then he didn't do a good enough job.

The series' director, Robert Alexander, told Insider that O'Neal's determination stood out in interviews.

"He's just incredibly determined, and he doesn't take any sort of — there's no back seat, there's no hesitation, no, like, he's gonna stop himself at a certain level when he wants something," Alexander said. "And he made that very clear of how he approached basketball, how he approached business then and now, and how he approaches life. He's not someone who settles on anything. If he wants something, he's gonna get it."

Alexander said that O'Neal's sheer presence in a room commands attention.

"His charisma in-person is overwhelming. It's incredible," Alexander said. "I mean, I think that he has such a strong personality and he has such ability to come into a space full of people, and not only just because his scale and his size, but how big his personality is and his ability to connect with people, how much he immediately controls a space. He is such a charismatic leader and owner of any space that he's in."

Indeed, O'Neal's presence looms large in the series — not just because it focuses on his life. Many of the interviews take place in a high-ceilinged, black room that features a giant silhouette of O'Neal dunking the ball — his personal logo.

According to Alexander, it's an indoor basketball court in O'Neal's house in Georgia. Alexander said the court is also decorated with O'Neal's stats and career achievements.

It seemingly appears in other interviews in the series.

In the series, O'Neal says he came up with the Shaq logo himself and trademarked it. When a marketing professor at LSU told him "Big men don't sell," O'Neal said he responded: "Fuck that. The whole world about to know my name."

"Shaq" debuts November 23 on HBO and HBO Max.