I can't really have a clue about what happened between him and Amber Heard. I just really have no idea. But I will say that there is no "typical" abuser. An abuser does not always start with a pattern of abuse with previous partners. There are all types of people who abuse their partner, from all different backgrounds, and partner abuse starts in all different ways. People can abuse one partner, then go on to the next partner and not abuse that new partner. There are statistical patterns but no hard and fast rules. All abusers are different people, and they all look different. They don't stop being an individual human being just because they are an abuser, they are still a unique person in many other ways. I also think that the idea that people are mostly consistent throughout situations in their lives is very, very problematic.
Now, back to the topic. Why does Johnny Depp suck?
He was very cute when younger, but although I find many men attractive who are no longer in the bloom of youth, he is not one of them. His flesh is washed out and sallow, he is bloated and tired looking. He is haggard. His teeth have not been looked after throughout his life and they are a mess. He does not glow with health and vitality. He looks poorly maintained in every respect. I find him physically very unappealing.
I have always enjoyed watching him in "Sleepy Hollow" but at the same time I felt like Christina Ricci had a much more difficult role in that film, his role seemed comical and exaggerated while she was required to be more convincing.
Some time ago, maybe about 7 years ago, I watched him in "The Libertine". Samantha Morton was in it and I felt that she made him look like the most incompetent actor on Earth. I have never wanted to follow his career after that because I felt as though I had a clear window into his incompetence. I must have imagined it, surely he could not have been that terrible. Maybe I would feel differently if I watched it again.