This query lists activities where a hard user delete has been performed.
CloudAppEvents
| where ActionType == "Hard Delete user."
| extend DeletedUser = parse_json(RawEventData).ObjectId
| project
Timestamp,
ActionType,
Application,
InitiatingUser = AccountDisplayName,
DeletedUser
CloudAppEvents
| where ActionType == "Hard Delete user."
| extend DeletedUser = parse_json(RawEventData).ObjectId
| project
TimeGenerated,
ActionType,
Application,
InitiatingUser = AccountDisplayName,
DeletedUser