There are a number of Event dispatchers that you can subscribe to.
All event dispatchers are located on the BPC_DamageSystem
component.
The below list details when each event is dispatched:
This triggers when damage is applied to a character
This triggers when a character is at or below 0 HP
This triggers when AoE radial hits are applied (regardless if it hits a character)
This triggers when healing is applied to a character
This triggers when incoming damage is blocked