@nik87 The anime shows that at no point was King's skin breached by Zoro's attacks. So the toughness/invincibility is due to the outer toughness, still does not explain how Jackpot functions though, is it a self explosion like Majin Vegeta or an outside of body explosion. The manga indicated that it was a self explosion through dialogue. Maybe King has instant regeneration or complete invincibility or both.