When in combat showdown, if a unit with deathknell is killed, does the deathknell trigger and resolve before healing or after?

In a combat showdown, Deathknell abilities resolve after the units are healed.

According to the official combat sequence (Rules 461.1, FAQ #9514, and FAQ #10157), the process is as follows:

1. Combat Damage Step: Combat damage is dealt to units (Rule 460.2).
2. Triggering Deathknell: Units with lethal damage trigger their Deathknell abilities. These triggers are added to the chain as Pending Items (Rule 808.1.d.2, Rule 323.4).
3. Killing Units: Units with lethal damage are moved to the trash (Rule 323.5).
4. Healing: All surviving units on the battlefield are healed (Rule 461.1.a.1).
5. Resolution: The game returns to the FEPR (Finalize, Execute, Pass, Resolve) process, and the Deathknell triggers that were added to the chain in Step 2 now resolve (Rule 808.1.d.3).

Key Implications

• Healing First: Because healing occurs in Step 4, any non-lethal damage on surviving units is cleared before your Deathknell effects resolve. You cannot use Deathknell effects to "finish off" enemy units that survived combat damage.
• No "Saving": Because units with lethal damage are moved to the trash in Step 3, Deathknell effects cannot be used to "save" a unit that took lethal combat damage.