I've done some thinking about this and developed XP guidelines for my setting, the relevant examples of which follow. These are a work-in-progress and I'm certain I'll tweak them over time.
1. Unambiguously defeating enemies--whether through killing, forcing their retreat, forcing their...
For what it's worth, here's what I decided for my setting when I found myself asking that same question (relevant section in bold):
"Destroying a lich's phylactery while the lich is still intact does no direct harm to the lich. However, the lich is well aware of the loss, and will usually...