Elon Musk’s biographer said the most painful thing in the billionaire’s life was his relationship with Amber Heard.

Walter Isaacson said on Kara Swisher’s podcast that “nothing hurt him more than that relationship.” Isaacson said the relationship was fraught with “storm and turmoil” that was “part of the attraction.”

Elon Musk’s biographer said the billionaire’s relationship with the actor Amber Heard hurt him the most — even more than Musk’s fraught relationship with his father.

“The storm and turmoil that both sides tell me about, this is not a matter of dispute, that was part of the attraction,” Walter Isaacson said on the latest episode of the “On With Kara Swisher” podcast. “Part of the theme of this life is this person is attracted to drama and storm. When things are calm, he surges — he buys Twitter or whatever. So, this is true of the relationship with Amber. Nothing hurt him more than that relationship.”

Musk and a lawyer for Heard did not immediately respond to requests for comment.

Musk and Heard dated on and off after bonding at the 2016 Met Gala. They took their relationship public in April 2017 before announcing their breakup a few months later. They continued seeing each other after their split before breaking up again in 2018.

Isaacson spent two years shadowing Musk for the biography, which hit shelves last week.

The book described a “psychological turmoil” in many of Musk’s romantic relationships. It recounted Musk’s and Heard’s first meeting: She asked if she could visit SpaceX a year after the two worked on the action film “Machete Kills,” Heard as a star and Musk as a consultant.

Isaacson also documented the explosive fights in their relationship, writing, “She and Musk would stay up all night fighting, and then he would not be able to get up until the afternoon.”

In the biography, Heard said she loved Musk “very much” but that “Elon loves fire and sometimes it burns him.”

When Isaacson asked Musk to explain his tumultuous romantic history, the billionaire replied, “I am often a fool, but especially for love.”

The Canadian musician Grimes, Musk’s ex with whom he shares three 𝘤𝘩𝘪𝘭𝘥ren, told Isaacson for the biography that Musk “associates love with being mean or abusive” in part because of his relationship with his father, Errol Musk.

Musk has said his father bullied and demeaned him throughout his 𝘤𝘩𝘪𝘭𝘥hood. In 2017, he told Rolling Stone his father was a “terrible human being” who had done “almost every evil thing you could possibly think of.”

Errol Musk has denied berating his son.

Musk’s first wife, Justine Wilson, to whom he was married from 2000 to 2008, has spoken about their relationship.

“There is a combative element to him,” she told Isaacson. “I don’t think you can be in a relationship with Elon and not argue.”

“When you’re from a dysfunctional background or have a brain wired like his,” Wilson told Isaacson, “intensity takes the place of intimacy.”