Simply put Kingpin, Black Iso8 debuff inflicted via his special 1 attack is reducing Offensive Ability Accuracy at a minimum (it may also just be reducing Ability Accuracy as a whole). This is in contradiction to the stated ability that Black Iso8 reduces Defensive Ability Accuracy.
*This is evidenced by Nick Fury being unable to place his bleeds while under Black Iso8’s effects.
Experienced in the Arena, likely not exclusive to the arenas.
Recorded on an iPad Air latest gen with current iOS and game build on wifi.
https://youtu.be/VKtDbB0AKsQ