How to format output

for having both in the same output row, you could potentially use `countif()`: https://docs.microsoft.com/en-us/azure/kusto/query/countif-aggfunction

let AuditLogs = 
    datatable(LoggedByService:string, ActivityDisplayName:string, Result:string)
    [
        "Self-service Password Management", "User started security info registration for self-service password reset", "success",
        "Self-service Password Management", "User started security info registration for self-service password reset", "failure",
        "Self-service Password Management", "User started security info registration for self-service password reset", "success",
        "Self-service Password Management", "User started security info registration for self-service password reset", "success",
        "Self-service Password Management", "User started security info registration for self-service password reset", "success",
        "Self-service Password Management", "Reset password (self-service)", "failure",
        "Self-service Password Management", "Reset password (self-service)", "failure",
        "Self-service Password Management", "Reset password (self-service)", "failure",
    ]
;
AuditLogs
| where LoggedByService == "Self-service Password Management"
| summarize SuccessCount = countif(Result == "success"), FailureCount = countif(Result == "failure") by ActivityDisplayName

  alternatively, if you want the output in the form of a property bag, you could use `make_bag()` on top of your original aggregation: https://docs.microsoft.com/en-us/azure/kusto/query/make-bag-aggfunction

let AuditLogs = 
    datatable(LoggedByService:string, ActivityDisplayName:string, Result:string)
    [
        "Self-service Password Management", "User started security info registration for self-service password reset", "success",
        "Self-service Password Management", "User started security info registration for self-service password reset", "failure",
        "Self-service Password Management", "User started security info registration for self-service password reset", "success",
        "Self-service Password Management", "User started security info registration for self-service password reset", "success",
        "Self-service Password Management", "User started security info registration for self-service password reset", "success",
        "Self-service Password Management", "Reset password (self-service)", "failure",
        "Self-service Password Management", "Reset password (self-service)", "failure",
        "Self-service Password Management", "Reset password (self-service)", "failure",
    ]
;
AuditLogs
| where LoggedByService == "Self-service Password Management"
| summarize count() by ActivityDisplayName, Result
| summarize Results = make_bag(pack(Result, count_)) by ActivityDisplayName