The Dallas-based natural gas and energy company originally entered into negotiations with Williams nearly 18 months ago, bidding $33 billion to purchase Williams outright.
Delaware courts ruled on Friday that Energy Transfer could back away from the deal after learning that investors would still be tied to tax liabilities.
Williams is now looking to file an appeal. The company believes Energy Transfer didn't have "the right to terminate the merger agreement," according to a statement cited by Bloomberg.
The deal is now one of many undone by dropping oil prices. Both companies lost significant market value in the past months, undermining the economics of the deal.
Bloomberg analysts added that Energy Transfer must still look for acquisitions in the coming months as the company has simply grown too big to support organic growth.
Shares of Williams Cos. are down 0.76% to $20.76 in afternoon trading.
Separately, TheStreet Ratings rated this stock as a "hold" with a ratings score of C.
The company's strengths can be seen in multiple areas, such as its increase in net income, good cash flow from operations and growth in earnings per share.
However, TheStreet Ratings also finds weaknesses including generally higher debt management risk, disappointing return on equity and a generally disappointing performance in the stock itself.
You can view the full analysis from the report here: ETP
Recently, TheStreet Ratings objectively rated this stock according to its "risk-adjusted" total return prospect over a 12-month investment horizon. Not based on the news in any given day, the rating may differ from Jim Cramer's view or that of this articles's author.