Who are the Heroes that Sweet Mask acknowledged?
Sweet Mask has acknowledged:


King (S-Class) - Chapter 93
He acknowledges King's split-second decision-making and fearless actions and even went so far as to say that there are S-class heroes serious about their jobs after all.
Feather (A-Class) - Chapter 94
He says that Feather is good and that he has star potential.


So, no, he not only acknowledges S-class heroes but A-class heroes as well.