Jiang Tianlin's flame was a secret technique recorded in the Taixuan Nine Chapters known as the Yin-Yang Profound Fire.
This fire had a peculiar property: the higher a person's cultivation level, the faster it burned them, and consequently, the quicker they died.
Xia Liu's cultivation was at the Fourth Layer of the Primordial Realm, whereas Yu Dabao was at the 5th Layer of the Primal Realm. Naturally, Yu Dabao died much faster.
Chapter 230