Black King
vs.
King Joe
Location: Kobe Bay (Ultraseven)
Rules: Original series feats only.
My verdict: Muahahahhaha.
Both have immense, Ultra-resistant durability. It took King Joe being shot by a special chemical to be destroyed. Black King, after resisting everything Jack threw at him, finally had his head severed by a rejuvenated Jack taking the Ultra Bracelet to King's neck. On the flip side these two monsters really take "the best defense is a good offense" and wipe their butts with it. King Joe is incredibly slow and generally a poor fighter, though he is physically strong. Black King is faster, but overall I don't see these two as being able to harm each other for literal years to come. Both of their beam weapons are puny as well. However, King Joe's ray he fires when separated is the strongest attack by either side. Without the later precedent showing that strong enough attacks (and presumably, enough attacks in the same spot) will destroy King Joe, plus Joe's edge in firepower and being a mechanical construct, I do think King Joe can outlast Black King. Perhaps he can choke out the monster/crush his skull as he attempted with Seven, or drown him in the bay. This fight does have the potential to take years.