According to Official Guinness Records,
The most cut diamonds set into one ring is 6,690, achieved by Vishal Agarwal and Khushbu Agarwal (both India), in Surat, India as verified on 9 May 2018. The ring had a flower design consisting of 36 individual petals.
For a complete list of 2018 records, please visit 2018 Guinness Records in India.