Which are all the S and A class heroes whom Garou fought? So far in the anime Garou has fought Tank Top Master, Heavy Tank Loincloth, Blue Fire, Magic Trick Man, Golden Ball and Spring Mustachio. From video segments of the manga I've seen he fought others such as


   Genos. 


Which are all the S and A class heroes whom Garou fought  ?
This will include spoilers of necessity.  I'll mention the webcomic appearances for S-class (I think the manga covers all of the A-class he fought in the webcomic already, but I won't quite guarantee it).  Though keep in mind there are differences between the webcomic and manga.

S-class


Metal bat
Genos
Bang
Watchdog Man
Tanktop Master
King (sort of)


In the webcomic he also fights:


   Everyone else except Blast, Metal Knight, and Drive Knight.  In several cases he fights three or more of them at the same time.


A-class


Blue Fire
Heavy Tank Loincloth
Magic Trick Man
Golden Ball
Spring Mustachio
Death Gatling
Smile Man
Stinger
Chain'n'toad


There's also a smattering of B-class heroes and even Mumen Rider, and a host of monsters that were classed as Demon or Dragon level threats.  A list of manga battles Garou has fought can be found here.