Any way to disable Instant-kill from enemies?

[Sakita]

instant-death, the ones that kill you outright instead of just leaving you knocked-out

[DozingDragon]

I do not believe so, but generally any instant-kill abilities require the character to be "Near Death" for the ability to actually instantly kill its target.  Disintegration also only kills its target if the character is knocked out  So keeping an eye on your party's health should allow you to mitigate the impact of those abilities.  Likewise, the very few enemies that can cause Injuries to party members without knocking them out can be countered by equipping and using Luminous Adra Potions to heal any Injuries.  

[Boeroer]

In some cases it helps to unequip the Grog pet.