When removing Namespaces are waiting for (already) deleted pods or deployments, there is something wrong…
But if you do not want to wait until the waiting is over, you can terminate the pod/deployment manually:
Run on the admin node:
NS=kubectl get ns |grep Terminating | awk 'NR==1 {print $1}' && kubectl get namespace "$NS" -o json | tr -d "\n" | sed "s/\"finalizers\": [[^]]+]/\"finalizers\": []/" | kubectl replace --raw /api/v1/namespaces/$NS/finalize -f -
Use of course at your own risk!