History
In order to finally rid the criminal world of the Punisher, the Kingpin managed to organize the crime families of New York City against him. Believing him to be defeated, Castle was invited to one of the Kingpin's safehouses to be 'taken care' of.
However, the Punisher had not given up and had instead made a deal with the Venom Symbiote. This deal was revealed to the Kingpin when the symbiote emerged from Castle's mouth, suffocating him.[1]