Responding to his $50 million (£38.3 million) defamation case against her, the actress, who was married to the "Pirates of the Caribbean" star for 15 months before she filed for divorce in May 2016, claims Depp repeatedly hit her, ripped out her hair and almost suffocated her.
Depp filed his suit earlier this year, revealing he took offence to a piece Heard wrote for The Washington Post, in which she described being the victim of domestic abuse.
She did not mention her ex by name, but he claimed she insinuated he was the abuser, insisting Heard's allegations were "a hoax."
Heard, 32, has now responded by going into lengthy details about the former couple's alleged fights in court papers exclusively obtained by the New York Post.
"About a year into our relationship, I began to witness Johnny abusing drugs and alcohol...," she writes. "On some occasions, when Johnny simultaneously used both illegal narcotics and prescription medications I have had to get him medical attention (sic)."
"Whenever he was using, I worried for both of us. He would become a totally different person, often delusional and violent. We called that version of Johnny, 'the Monster'."
Heard went on to claim her ex would often "not remember his delusional and violent conduct after he came out of his drunk or medicated states", adding, "Because I loved Johnny, I had believed his multiple promises that he could and would get better. I was wrong."
Recalling a private jet flight from Boston to Los Angeles in May 2014, the actress claims Depp appeared to be drunk.
"On the flight, Johnny ordered the flight attendants to give him an oxygen tank, and drank heavily," she writes. "Johnny's handlers told me that he was upset that I was filming a movie with a romantic scene with James Franco the day before."
"Soon, Johnny began to throw objects at me. Instead of reacting to his behavior, I simply moved seats. That didn't stop him. He provocatively pushed a chair at me as I walked by, yelled at me, and taunted me by yelling out the name 'James Franco'."
"At some point, I stood up, and Johnny kicked me in the back, causing me to fall over. Johnny threw his boot at me while I was on the ground. Johnny continued to scream obscenities until he went into the plane bathroom and passed out locked in the bathroom for the remainder of the flight."
He allegedly apologised later via text, writing, "Once again, I find myself in a place of shame and regret. Of course, I am sorry. I really don't know why or what happened. But I will never do it again."
"My illness somehow crept up and grabbed me... I must get better... Again, I am so sorry, so sorry... I love you and I feel so bad for letting you down."
Heard goes on to claim she locked herself in a room a month into the marriage, during a heated argument with her husband over his alleged use of the drug ecstasy during a bender in Australia.
"The argument heated up, and Johnny pushed me, slapped me, and shoved me to the ground before I retreated to a locked bedroom," she writes. "(The next morning) I went downstairs to find that Johnny was still awake, and that he had stayed up all night, having taken about eight MDMA pills. He was also drinking again. We got into a fight that Johnny made physical, and I barricaded myself in one of the rooms. That didn't stop Johnny from busting through the door of the room I was in...."
Heard alleges the incident dragged on and left her completely terrified. "In one of the most horrific and scariest moments of this three-day ordeal, Johnny grabbed me by the neck and collarbone and slammed me against the countertop," she states. "I struggled to stand up as he strangled me, but my arms and feet kept slipping and sliding on to the spilled alcohol and were dragged against the broken glass on the countertop and floor, which repeatedly slashed my feet and arms."
"Scared for my life, I told Johnny, 'You are hurting me and cutting me.' Johnny ignored me, continuing to hit me with the back of one closed hand, and slamming a hard plastic phone against a wall with his other until it was smashed into smithereens. While he was smashing the phone, Johnny severely injured his finger, cutting off the tip of it... Once I was able to get away, I barricaded myself in an upstairs bedroom."
Depp, she claims, was hospitalised for his finger injury, while she states she was left with "a busted lip, a swollen nose, and cuts all over my body," adding, "I still have scars on my arms and feet from this incident."
In the new court filing, Heard also claims she lashed out at Depp in March 2015 because she feared he was about to attack her sister, Whitney, and Johnny "picked a fight with me" during a trip to Thailand and Malaysia in August 2015, adding, "While on the Eastern Oriental train... he started hitting and pushing me against a wall by grasping my throat and holding me there. I remember being afraid that Johnny might not know when to stop, and that he might kill me."
There were other alleged violent moments in December 2015, and Heard resolved to leave Depp for good and filed a request for a domestic violence restraining order after he allegedly attacked her in May 2016, when he allegedly threw a phone in her face "as hard as he could."
"Johnny grabbed my hair and started to slap, shake and yank me around the room while I continued to scream," she states.
Depp and his representatives have yet to respond to his ex-wife's latest filing, but in his defamation lawsuit, his lawyers declared, "Mr. Depp never abused Ms. Heard. Her allegations against him were false when they were made in 2016. They were part of an elaborate hoax to generate positive publicity for Ms. Heard and advance her career."