argo-cd/docs/user-guide/app_deletion.md

App Deletion

Apps can be deleted with or without a cascade option. A cascade delete, deletes both the app and its resources, rather than only the app.

Deletion Using argocd

To perform a non-cascade delete:

argocd app delete APPNAME --cascade=false

To perform a cascade delete:

argocd app delete APPNAME --cascade

or

argocd app delete APPNAME

Deletion Using kubectl

To perform a non-cascade delete:

kubectl delete app APPNAME

To perform a cascade delete set the finalizer, e.g. using kubctl patch:

kubectl patch app APPNAME  -p '{"metadata": {"finalizers": ["resources-finalizer.argocd.argoproj.io"]}}' --type merge
kubectl delete app APPNAME 

About The Deletion Finalizer

For the technical amongst you, the Argo CD application controller watches for this finalizer:

metadata:
  finalizers:
    - resources-finalizer.argocd.argoproj.io

Argo CD's app controller watches for this and will then delete both the app and its resources.

When you invoke argocd app delete with --cascade, the finalizer is added automatically.