What are the top 10 most notable corporate bankruptcies this year?

As an AI language model, I can provide information up until September 2021. Here are ten notable corporate bankruptcies that occurred in 2021:

1. Hertz Global Holdings: The car rental company filed for bankruptcy in May 2020 but emerged from it in 2021 after restructuring.
2. Frontier Communications: The telecommunications company filed for bankruptcy in April 2020 and emerged in April 2021 after reducing its debt burden.
3. The McClatchy Company: A major newspaper publisher filed for bankruptcy in February 2020 and exited in September 2020 after transferring ownership to hedge fund Chatham Asset Management.
4. J.C. Penney: The retail chain filed for bankruptcy in May 2020 and emerged in December 2020 after being acquired by Simon Property Group and Brookfield Asset Management.
5. Neiman Marcus: The luxury department store filed for bankruptcy in May 2020 and emerged, under new ownership, in September 2020.
6. Brooks Brothers: The clothing retailer filed for bankruptcy in July 2020 and was acquired by Authentic Brands Group, which relaunched the brand.
7. Lucky Brand: The apparel retailer filed for bankruptcy in July 2020 and was acquired by SPARC Group LLC.
8. GNC Holdings: The health and nutrition company filed for bankruptcy in June 2020 and emerged in September 2020 after being acquired by Harbin Pharmaceutical Group.
9. Pier 1 Imports: The home furnishings retailer filed for bankruptcy in February 2020 and completed its liquidation and closure by the end of the year.
10. Chesapeake Energy: The natural gas producer filed for bankruptcy in June 2020 and emerged from it in February 2021 after reducing its debt and restructuring operations.

Note that bankruptcies can evolve, and the status of some companies may have changed beyond these details.