YouTube has released their most popular cover parts. Cover makes both artists famous and is helping to promote the music of the original artist. According to the result of YouTube list most Adele songs. 

List of the most ever cover 
song as follows:

All of Me   John Legend 

Love Yourself   Justin Bieber 

Someone Like You   Adele 

Hello   Adele 

Stay With Me   Sam Smith 

The Scientıst   Coldplay