What sickness did the alliance chief have?
Kang-Sung took some "deadly" hits during his fight with Goomonryong.

He couldn't always use his reflection technique to counter the attacks, first example in chapt 142 by kicking him in the air.

After that he took a huge amount of hits, Goomonryong is strong enough to destroy a building so.. imagine the effect on a human :)

Imo the final hit chapt 143 is the one that caused the more damages.