Which American heavy metal singer, nicknamed "Ripper" from the Judas Priest song, "The Ripper", performs alongside guitarist Yngwie Malmsteen on his 18th studio album, "Relentless"?
Relentless (Yngwie Malmsteen album): Relentless is the eighteenth studio album by guitarist Yngwie Malmsteen, released on November 23, 2010, through his independent label Rising Force Records.
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