From https://en.wikipedia.org/wiki/Masood_Azhar
Starting 2009, there have been 4 attempts to put Masood Azhar in the UN Security Council's counter-terrorism sanctions list. All the attempts were vetoed by China, citing 'lack of evidence'. China moved to protect Azhar again in October 2016 when it blocked India's appeal to the United Nations to label him as a terrorist. China also blocked US move to get Azhar banned by UN in February 2017. The most recent attempt was on 13th March 2019. However, China pulled the blockade in May 2019, finally resulting listing of Masood Azhar as a global terrorist.