During his conversation with Rashad Bilal and Troy Millings, the hosts of Earn Your Leisure podcast, Ice Cube unequivocally proclaimed his 1991 record "No Vaseline" as the best diss track of all time. 

Around the 1:12:00-mark, Cube noted how his searing track was "one of the top battle songs ever," and elaborated on why he considers that the case. He mentioned some of the other top diss tracks including, 2Pac's "Hit Em Up," Nas' "Ether," Boogie Down Productions' "The Bridge is Over," and Kool Moe Dee's "Let's Go," but made it clear that none of them "come close" to what he did with "No Vaseline." 

While it was pointed out that "Ether" laid waste to the entirety of Roc-a-Fella, Cube said "I broke up a group! That was kind of the beginning of the end for Ruthless."

Source: Youtube.com