My hand pierces through the Core Disciple's chest and I take out his heart in the process.
Now, he is dead.
I incinerated the Core Disciple's heart using Fire Dao as the flames enveloped and burnt the heart into nothingness. Even the ashes were burnt.
I proceed to cremate the Core Disciple's corpse and with the sword art form of the Sword Of Fire, Hell's Punishment, the flames cremated the corpse along with the Core Disciple's soul.
The Core Disciple's soul was as strong and durable as a Monarch Realm cultivator's soul and it must be due to the Core Disciple's identity as a transmigrator. Nevertheless, the flames still burnt the Core Disciple's soul into nothingness despite the durability of his soul.
Transmigrators and reincarnators have a higher probability compared to other living beings in terms of tricking the cycle of reincarnation so if I didn't burn the Core Disciple's soul, he might transmigrate again with his memories intact.