Answer
Errol Spence Jr. defeated Kell Brook to win the IBF title in 2017. This was a major upset, as Brook was considered to be the favorite going into the fight. Spence Jr. dominated the fight from start to finish, knocking Brook down three times before the referee stopped the fight in the 11th round. This victory solidified Spence Jr.'s status as one of the top welterweights in the world.