Best Buy CEO (Lucas Jackson | Reuters)

Some of these guys repeatedly made bird-brained business decisions, while others did things that were ethically backward or out-and-out illegal. But the one thing they all lacked? The quality bosses need the most: leadership. Luckily, you can learn from the mistakes of these CEOs and avoid their failings to pave your path to the top. (On the flip side, here are 6 Things All Great Bosses Know.)


5. Rodrigo Rato, President of Bankia (Spain)
Imagine if in addition to the U.S. government giving billions of dollars in loans to banks during the financial crisis, they also allowed seven already too-big-to-fail institutions to merge into one "megabank"--which managed to lose over $4 billion in a single year. That's essentially the story behind Bankia and the man put in charge, former high-ranking government finance minister Rodrigo Rato.

The lesson:Past performance doesn't predict future success.

"Most evidence points to Rato being a capable guy, and it's possible he wanted to believe that Bankia was going to be successful," says Finkelstein. It's like when you come out of college with your stellar GPA and glowing recommendations from professors. Don't expect to ride your undergrad accomplishments all the way to the top--you'll have to prove yourself again and again throughout your career, Finkelstein says. Once you've done that, know the right way to ask for a bigger slice of the pie. Click here for 30 Tips to Save More Money and Earn a Raise.

4. Mark Pincus, CEO of Zynga
Pincus is the founder of Zynga, the video game company responsible for clogging up your Facebook feed with titles like "Farmville" and "Mafia Wars." And although those games are gaining users, Zynga's stock has bottomed out 85 percent lower than its highest price. Not surprisingly, many top execs have fled the company--most likely because Pincus' background is as an entrepreneur, not a team-playing business executive. "As a CEO, you can't run a large company alone," says Finkelstein.

The lesson:Learn to delegate.

With any promotion you'll suddenly be in charge of a handful of underlings, all tasked with the same role you were once doing better than anyone else. Resist the urge to do your subordinates' job for them. "Set high goals and expectations, hold them accountable, and most importantly, get out of the way," says Finkelstein.

3. Andrea Jung, Chairman of the Board at Avon (resigned in April 2012)
Before she resigned as CEO, Jung had been running cosmetics giant Avon since 1999. "She thought she was the company," says Brian Sozzi, Men's Health Million Dollar Man blogger. But Avon is currently under investigation by the Securities and Exchange Commission for possibly paying bribes in China. You could blame Jung's marketing and branding background, which may have served her well in established markets, but didn't prove up to the task when navigating China's complicated economy and political system, Finkelstein says.

The lesson:Fill your knowledge gaps.

"Just because you're an expert in one area doesn't mean that necessarily translates to a related field," says Finkelstein. There are many ways to keep your brain sharp, including thought-provoking books, free seminars, conferences, and even continuing education classes at your local college. Your company may even reimburse the cost of additional professional training, so check in with human resources before you take out your debit card.

2. Aubrey McClendon, CEO of Chesapeake Energy (resigned as chairman but remains CEO)
McClendon's sins as CEO of Chesapeake Energy are numerous. The biggest of them all: With a 19 percent stake in the Oklahoma City Thunder, McClendon arranged for Chesapeake to sign a $36 million sponsorship deal, along with $4 million annually for the naming rights to the Thunder's home court. "You may love Kevin Durant, but you can't get your company to financially support the basketball team that enriches you as a team owner," Finkelstein says.

The lesson:Follow the rules.

Plenty of powerful politicians and business leaders fall from grace by thinking they're above the law, Finkelstein says. Young guys farther down the totem pole are also guilty, from fudging expenses to abusing break times. Stick to the guidelines in the employee handbook (lame as they may be), and you'll be a role model to your peers and trusted by your supervisors.

1. Brian Dunn, former CEO of Best Buy (resigned in April 2012)
Dunn admirably worked his way up from the sales floor to running the entire company. But maybe all that time immersed in one corporate culture explains why Best Buy seems continually blindsided by cheaper online rivals like Amazon. "He forgot to look ahead into the longer term, which is a very important thing as a CEO," says Sozzi. To top it off, it was revealed that the married Dunn was having an affair with a 29-year-old Best Buy employee.

The lesson:Don't play favorites.

Sleeping with one of your employees doesn't necessarily mean you're giving them an unfair advantage in the office--but everyone is going to think that. Don't forget: A subordinate who's a regular drinking buddy can be just as poisonous to the workplace as a sexual partner. "It sets the standard about your ethics," says Finkelstein. Politely keep your relationship with your boss professional, and once you're in charge, don't look to the office as a pool of friends or hookups. (Office relationships are common--but are they worth it? Find out in the special report Sex In the Office: Worth the Risk?)