The explosion greatly reduced both Jack and Spring Crown's HP. But Jack was protected by both the Lightning God Suit and Gold Scale Armor, plus his HP was exceptionally high. Spring Crown had no such advantage, his HP was completely depleted.
However, Spring Crown's HP stopped at 1. Jack had expected it, though. These Heavenly Enforcers often carried a sacrificial dummy.
Jack gave Spring Crown a quick attack that took out that remaining 1 HP. Unfortunately, the Lightning God Suit's Paralyze effect didn't hit at that last second. Before the last attack hit, Spring Crown expertly exchanged his pendant for an amulet of rebirth. The fellow was even smiling when Jack's killing blow landed.
It was a pity, Jack thought, but at least he forced this guy to waste his amulet of rebirth. Spring Crown would need more coins to pay for the next one.