“Karma is relentless, and it caught up with Mr. Mitchell,” a former Deutsche Bank executive told me.

The executive, Mike Offit, was referring to the fiery death in 2000 of Edson Mitchell, one of the German bank’s most prominent leaders. Offit and Mitchell had clashed—according to Offit, Mitchell had ousted him for no good reason—and when Mitchell’s small plane crashed into a Maine mountain a few days before Christmas, Offit saw cosmic justice. Nearly two decades later, he was still nursing resentments toward the dead man.

I’ve been writing about banks and Wall Street for the better part of two decades, and along the way I’ve seen my share of backstabbing, mayhem, and pure meanness. From 2007 until 2010, for example, I was the Wall Street Journal reporter responsible for covering Citigroup. The financial crisis was in full swing, and the giant bank was unraveling in spectacular fashion. I had cultivated good sources inside Citigroup, and they would frequently call me late at night to vent, off the record and perhaps a little drunkenly, about their colleagues. They accused each other of being indecisive, reckless, cocky, greedy, and just plain stupid. I assumed I would never again witness anything remotely as dysfunctional as crisis-era Citigroup.

I was wrong.

Double-Crossing in the Deep

For the past two years, I’ve been immersed in Deutsche Bank as I reported and wrote my new book, Dark Towers. I interviewed roughly 200 people, including scores of current and former bank executives, employees, and board members. And in this process, I heard about so much treachery that I’ve concluded it is one of the defining traits—almost an organizing principle—of the disgraced German bank.

A few examples:

  • A top executive, furious at being passed over for a plum job, set out to sabotage the bank’s C.E.O. by convincing regulators to torpedo the promotion of a close friend.
  • A number of executives told me that one of the bank’s highest-ranking officers hired spies to eavesdrop on colleagues.
  • One senior executive apparently had a habit of leaking damaging personal information about his internal rival to a New York tabloid.

On multiple occasions, various senior executives trashed various colleagues to me, then called those colleagues and assured them that they had just sung their praises or defended them. Then those colleagues proceeded to bad-mouth the senior executives who claimed to have been helping them. Round and round we went.

Even board members—supposedly the grown-ups in the room, the figures responsible for policing the conduct of more impulsive executives—have accused each other and their subordinates of cover-ups and ineptitude.

And that’s not to mention what former Deutsche Bank employees told me was routine sexual misconduct, anti-Semitism, and racism. Why were they sharing this dirty laundry with me? Because Deutsche has become a poster child for everything that’s wrong with modern capitalism and, arguably, the world’s most dangerous and destructive bank. Just about everyone who’s been connected to it—including some of its former C.E.O.’s—is desperate to wash his hands of responsibility.

Treachery is one of the defining traits—almost an organizing principle—of the disgraced German bank.

How bad are things? Deutsche Bank’s shares have fallen more than 90 percent from their peak, in 2007. Many investors and regulators doubt the bank’s ability to survive. Look at just about every financial scandal of the past decade, and Deutsche Bank has been smack in the middle: manipulating markets; violating international sanctions; laundering money; dodging taxes; misleading investors, customers, and regulators.

Oh, and it was the only mainstream financial institution consistently willing to do business with Donald Trump. By the time he was sworn in as president, he had borrowed a total of more than $2 billion from Deutsche Bank, of which roughly $350 million was still outstanding. In other words, this was a company not known for its responsible decision-making or strong corporate culture.

Birthday Plans: Staying Afloat …

This year marks Deutsche Bank’s 150th anniversary. For its first 12 decades, Deutsche was a relatively conservative European lender. Then, in the late 1980s, it developed a taste for Wall Street. When I started working on Dark Towers, I figured it would end up being a relatively straightforward tale of greedy investment bankers and traders running roughshod over a responsible, old-fashioned German bank. But it wasn’t nearly that simple.

Yes, the Wall Street guys were out of control. They pushed the bank into all sorts of risky products and businesses that would be the source of heartburn for years to come. They rigged markets and ripped off customers and infected the bank with a reckless, amoral culture. But in many ways it was the Germans who did the bank in. They signed off on costly and ultimately disastrous acquisitions. They gave a bunch of Wall Street traders and salesmen carte blanche to hire whomever they wanted and then to do whatever they wanted with a huge budget. They didn’t make a serious effort to monitor, much less rein in, some of the over-the-top activities happening on Wall Street.

That is not to mention what former employees told me was routine sexual misconduct, anti-Semitism, and racism.

Humans respond to incentives, and the incentives at Deutsche Bank—dictated from the very top of the institution—were crystal clear: make as much money as possible, as quickly as possible, consequences be damned. Without strong leaders who were willing to make the difficult decisions to forgo easy profits, to stand up to the guys who were always pushing the envelope, it’s no surprise that Deutsche Bank descended into every-employee-for-himself anarchy. And it’s easy to draw a straight line from that culture to the backstabbing that I witnessed as I tried to sort out who was responsible for the mess.

As it turned out, there was more than enough blame to go around.

David Enrich’s Dark Towers: Deutsche Bank, Donald Trump, and an Epic Tale of Destruction is out now from Custom House