User blog comment:Da1dx/Who has the best Spark vuln. Debuff?/@comment-24277289-20161024160006

Demolishing Roar Rutheon gives 50% Spark vulnerability on his SBB, the highest SBB boost in the game. I think Zero is the highest for Spark vulnerability with 150% vulnerability. Fun fact, Rutheon also gives the highest SBB crit Spark damage up at 100%