Both are serious
Setting Hueco Mundo
Baraggan with mid difficulty. Bankai Ichigo was able to react to the extension of the blade after seeing it a few times (both when Gin was using his Bankai techniques - Buto and Buto Renjin) and when he put on the mask, he was even able to dodge Buto Renjin. Baraggan casually speedblitzing Soifon to the point that she had no idea where he came from tells me that he'll react to KnY.
KnY will never touch him due to time dilation field + aging via physical contact. Constantly spamming Respira also means that once the blade approaches Baraggan, it's gone. Gin's Zanpakuto gets aged away and he'll no longer have a weapon to fight Baraggan.
After decades the 'blackout' rule may be coming to an end.