The most effective form of media sanitization to ensure residual data cannot be retrieved is destroying. Media sanitization is the process of removing or destroying the data stored on a physical or logical media, such as a hard drive, a flash drive, or a cloud storage, to prevent unauthorized access or disclosure. Destroying is the most extreme form of media sanitization, which involves the physical destruction of the media, such as shredding, crushing, melting, or incinerating. Destroying can ensure that the residual data cannot be retrieved by any means, as the media is rendered unusable and irreparable. Destroying is usually applied to the media that contains highly sensitive or classified data, or the media that is no longer needed or functional.
References: CISSP All-in-One Exam Guide, Eighth Edition, Chapter 2: Asset Security, page 69; [Official (ISC)2 CISSP CBK Reference, Fifth Edition, Chapter 2: Asset Security, page 131]