Its become clear in recent times how some financial institutions were noticeably less prudent than others. Sometimes its obvious that mistakes were made, things were rushed and for whatever reason proper procedures not followed. Sometimes it may have been excused by an oversight, or by the "wink wink" , or a rush to get things done by a bank holiday weekend, or the borrower being a friend / acquantaince, or the lender geting a bonus / kickback, lack of experience of the lender or whatever. I remember one particular lender diversifying in to an area ( commercial lending through brokers ) they had no experience in, and little expertise as it proved. I would image lending staff sometimes got commission / bonuses / promotion for reaching or exceeding targets they advanced?
To answer the OP's question, the most shameful lending I know of is a loan for 90 times the persons income. The borrowers own bank did not give him a loan at all when he asked for one, but another bank lent a 7 figure sum which was over 100% of the property cost, for 90 times his income. The borrower (who was medically unwell ) had closed down his old business / sold old stock etc, and the broker knew that, but the financial institution either did not know or did not care. Should'nt the financial institution have phoned up / checked to see if the borrower had the means to make 20 years of monthly repayments? The building society used a "buy-to-let" mortgage application form, for this 209 year old property! No proper valuation was done - the valuation which was done valued the property ( a derelect property of an eleventh of an acre in the west of Ireland ) at 17 million an acre! The nearest record within a 130 mile radius was a fraction of that. The borrowers life has been destroyed since, and his life made a hell. Sleepless nights, 7 years without holidays or new clothes, losing assets built up over many years, secondhand Santy toys, a miserable lifestyle and future etc
No wonder many of the banks and building societies in Ireland got in to so much trouble, and destroyed the country in the process. Not all financial institutions acted imprudently or shamefully though. Some "bankers" have a lot to answer for. None have gone to jail and few have lost their jobs or pensions as a result of their mistakes. Not yet anyway.
The banks and building societies had a duty of care to their customers, and to society in general. After all, society has bailed them out. The financial institutions should have ensured loans were sustainable and the borrower had the capacity to make 20 years monthly repayments if that was the terms of the loan. They should have ensured that the property was fairly and properly valued by a competent, qualified and experienced valuer, not known to the property vendor, buyer etc.
In a hypothetical case, if a man off the street was mad enough to want to pay 200k for a secondhand ford fiesta, and was enticed by an interest only loan for the first few years, the financial institution should not lend 210k if his salary was 4k. The financial institution should have checked to see if the figures added up before lending the money. The man off the street was not the financial expert : it was the banks job to evaluate his ability to meet monthly repayments over the term of the loan, and the bank should not lend money to be repaid over 20 years when it knows it will not be repaid over 20 years. And the secondand fiesta should not have been valued at 200k if other fiestas were worth nothing like that - even if the valuer knew the borrower well, and the borrower wanted that particular fiesta.
The truth will out yet, and thank God it will. If it does not, bankers will repeat the same mistakes again at some point in the future. We must all learn from the past. Some have not felt the pain yet.