The mistreatment of a couple in mortgage arrears and the wrongful loss of a no-claims bonus are among the 127 cases that were investigated and either partially or substantially upheld by the Financial Services and Pensions Ombudsman (FSPO) last year.
Ger Deering has for the first time published in full 228 legally binding decisions arising from 234 formal investigations he carried out in 2018.
The cases were published so the public can see the kinds of problems arising in the sector and the power his office has to remedy them.
Mr Deering said 107 of the cases he investigated were not upheld.
According to the FSPO, the vast majority of the complaints he investigates are successfully resolved through informal mediation, with 2,300 settled this way last year, often by phone.
"However, it is clear from the decisions I am publishing today that some providers do not always act in the best interest of their customers," Mr Deering said in a statement.
"I have found that it is still the case that some providers are not willing to listen to or engage sufficiently with their customers in order to resolve disputes."
"Where disputes are not resolved by agreement, I will continue to use the extensive powers available to me to investigate and adjudicate complaints in a transparent and impartial manner to ensure fairness and, where necessary, to direct providers to pay compensation or rectify their conduct," he added.
The cases include one where a couple, whose mortgage provider adopted an obstructive approach after they fell into arrears on a buy-to-let mortgage, were awarded €90,000 in compensation.
In another case, an insurance company stripped a customer of their no-claims bonus after he was involved in a crash caused by an uninsured driver.
The FSPO awarded compensation of €3,000 to the policy holder.
Another individual received €7,000 in recompense when a lender failed to inform him that a loan he had taken out had not been completely paid off, even though it stopped deducting direct debit payments.
This led to the borrower's credit record at the Irish Credit Bureau being tarnished and it was subsequently ordered by the FSPO to correct its records.
The FSPO is the statutory authority with the power to investigate complaints relating to insurance, banking, credit facilities and investments, as well as pensions.
It opened for business at the beginning of last year, after the merging of the offices of the Financial Services Ombudsman's Bureau and the Office of the Pensions Ombudsman to form the FSPO.
Prior to the enactment of the Financial Services and Pensions Ombudsman Act in 2017, the Financial Services Ombudsman's Bureau did not have the power to publish its legally binding decisions.
The Ombudsman can direct a provider to pay compensation of up to €500,000 to a complainant.
He can also order a provider to rectify the conduct that led to the complaint in the first place, with no limit on the value of that rectification.
Other cases listed among the more than 200 published today include the payment of compensation of €250 to a person whose travel insurance policy was automatically renewed and who was subsequently refused a refund when she tried to cancel the policy.
A customer, whose bank opened a new account for her without her knowledge or consent, also received compensation of €3,750.