(Reuters) -A consortium led by Abu Dhabi National Oil Company on Wednesday withdrew its $18.7 billion offer to buy Australian gas producer Santos after months of wrangling over valuation and terms.

The third failed bid for Santos in seven years underscores the hurdles to getting big transactions across the line in Australia, where disagreements over valuation, shareholder approval thresholds and regulatory risks have repeatedly derailed mega-deals.

Here is a list of some of the biggest failed mergers and acquisitions involving Australian companies over the past three years.

ADNOC-SANTOS

A consortium led by Abu Dhabi's ADNOC scrapped its $18.7 billion bid for Australia's Santos, saying commercial terms could not be agreed.

XRG, ADNOC's overseas unit, pulled the offer saying "a combination of factors, when considered collectively, have impacted the Consortium's assessment of its indicative offer."

Santos said the consortium refused to agree to a fair sharing of risk, including taking responsibility for securing regulatory approvals and committing to domestic gas development and supply.

The XRG-led consortium in June proposed to offer $5.76 a share, which was A$8.89 at the time. Santos last traded at A$6.74.

BHP-ANGLO AMERICAN

Australia's BHP Group ( BHP ), the world's largest miner, walked away from a $49 billion bid to acquire rival Anglo American in May 2024 after it was rebuffed three times.

The structure of BHP's deal, which required Anglo to unbundle its South African platinum and iron ore businesses, was a major reason for its collapse.

BHP's offer valued Anglo at 29.34 pounds per share. Anglo American last traded at 25.18 pounds.

WOODSIDE-SANTOS

Australia's Woodside Energy ( WDS ) and smaller rival Santos ended talks in early 2024 to create a possible A$80 billion ($53.15 billion) global oil and gas giant.

According to sources, the talks fell through because the two companies could not agree on a valuation level.

BROOKFIELD-ORIGIN ENERGY

Canadian investment firm Brookfield's joint $10.6 billion takeover bid with MidOcean Energy for Origin Energy ( OGFGF ) failed in late 2023, after only 69% of the shareholders in the Australian power retailer voted in favour of the deal, below the required 75% threshold.

Brookfield offered A$9.53 a share. Origin last traded at A$12.41.

ALBEMARLE-LIONTOWN RESOURCES

U.S.-based miner Albemarle dumped an A$6.6 billion ($4.39 billion) buyout bid for Australian lithium developer Liontown Resources ( LINRF ) in 2023, in part because of "growing complexities" around the transaction.

Albemarle proposed to offer A$3 a share. Liontown last traded at 91 Australian cents a share.

KKR-RAMSAY HEALTH CARE

A group led by private equity firm KKR & Co ( KKR ) withdrew a nearly $13 billion bid for Australian hospital operator Ramsay Health Care ( RMSYF ) in 2022, after talks hit a stalemate.

Ramsay said the KKR group had cited the company's weak business performance while deciding not to sweeten its offer.

Sources told Reuters that KKR had not been able to gain access to the accounts of Ramsay's European unit, Ramsay Sante, to carry out due diligence.

KKR offered A$88 a share. Ramsay last traded at A$32.95.