But if the banks were remorseful and apologetic, they had a funny way of showing it.
Despite their contribution to the global financial meltdown, they continued to operate as if nothing had changed.
The billions of taxpayer dollars spent bailing out their "casino" activities somehow ended up further enriching them; they pocketed obscene bonuses while the casualties of their handiwork lay all around them.
They couldn't seem to lose. For example, Goldman Sachs was found to have sold mortgage-related securities that were designed to fail so that a large hedge fund could bet against them.
When the securities failed as planned, the hedge fund collected $1 billion in profits.
Goldman Sachs was fined US$550 million for that transgression, but that was nothing compared to the killing they made after American taxpayers bailed out AIG, thereby allowing AIG to pay out nearly US$12 billion to Goldman Sachs for similar bets that AIG had insured.
The latest banking scandal emerged last week when American and British regulators fined Barclays Bank £290 million ($568 million) for interest rate fixing between 2005 and 2009.
More global banks are under investigation.
As penance, Diamond and his top lieutenants have offered to waive their bonuses for the year, but I imagine the £17 million Diamond took home in 2011 (despite shareholder protests, and against a dramatic fall in the bank's share price and return on equity) will keep the wolves from his door for a little while.
There's been a loud chorus of condemnation for the "massive cesspit" exposed by the scandal - the "swaggering arrogance", "revolting laddishness", and "blithe disregard for regulations".
The Governor of the Bank of England, Sir Mervyn King, has accused the banking industry of immorality, "excessive levels of compensation ... shoddy treatment of customers, [and] deceitful manipulation of one of the most important interest rates". He called for "a real change in the culture" of the industry.
Commentators say the industry needs to dump its "bonus culture" for an "ethical culture", that it needs to "re-moralise".
Fat chance.
I'm not sure why everyone seems so surprised to find that the financial sector is full of hubristic, self-interested individuals who aren't overly fussed with ethical behaviour. Isn't this the logical extension of the dominant economic theory that holds that we're just self-interested hedonists and the world would be a better place if we left the common good to the market?
British financial commentator Anthony Hilton told the Independent that it all started to go wrong "20 years ago when we imported the American idea that business was only about making a profit".
"The logical next step was to give key employees extra money if they could boost revenues. The mistake was to assume that a bonus would make people work harder when it simply makes them work differently. Customers got exploited, services got cheapened, ever bigger risks were taken.
"And it seemed to work because profits appeared to go up, but we now know this was only because the long-term cost - the undermining of the integrity of the business - stayed hidden until it erupted into the full-blown crisis we now have. Today's problems will not go away as long as the bonus culture and the blind pursuit of short-term profit remains."
There's no suggestion of the same excesses in our banks. Still, in 2009, our four main (Australian-owned) banks reached a settlement with Inland Revenue for a combined total of $2.2 billion after two of them were convicted of tax evasion.
Last year, those same banks posted a combined total profit of more than $2.7 billion. Not bad for recessionary times. After the market-fixing scandal, British politicians are making noises about bringing back regulations designed to rein in excess.
Deregulation in Britain during Maggie Thatcher's reign with the "big bang" reforms of 1986, and in the US, with, for example, the 1999 repeal of the 1933 Glass-Steagall Act, which had previously split investment banking from ordinary retail banking, had given bankers free rein.
Even Adam Smith, the "patron saint of laissez-faire capitalism", knew that was a bad idea.
As Gareth Morgan and Susan Guthrie write in The Big Kahuna, "Smith decided that when wealth became concentrated in the hands of the few, they gained political power and economic privileges which interfered with the free operation of the markets ... he blamed the widening gap in income and wealth on collusion among the owners of capital. The man had undergone the effects of a revelation - one that still awaits our modern day champions of 'unfettered markets'."