After 21 straight Wrestlemania victories, Undertaker finally lose to Brock Lesnar at Wrestlemania 30
This was an epic night to remember because the Wrestlemania undefeated streak ended when Brock Lesnar defeated the Undertaker at Wrestlemania 30. After a methodological match, Brock finally pinned the Phenom right in front of 75,000+ spectators who were stunned during the event in Mercedes-Benz Superdome, New Orleans.
Will Undertaker finally retire? Well 21 Wrestlemania victories are long enough so I think he should take a rest.
Source: http://www.wwe.com/shows/wrestlemania/30/undertaker-brock-lesnar-26184576