When you are finished with your Apache Kafka cluster, you can delete it by running:
kubectl -n kafka delete $(kubectl get strimzi -o name -n kafka)
This will remove all Strimzi custom resources, including the Apache Kafka cluster and any KafkaTopic custom resources but leave the Strimzi cluster operator running so that it can respond to new Kafka custom resources.
Next, delete the Persistent Volume Claim (PVC) that was used by the cluster:
kubectl delete pvc -l strimzi.io/name=my-cluster-kafka -n kafka
Without deleting the PVC, the next Kafka cluster you might start will fail as it will try to use the volume that belonged to the previous Apache Kafka cluster.
When you want to fully remove the Strimzi cluster operator and associated definitions, you can run:
kubectl -n kafka delete -f 'https://strimzi.io/install/latest?namespace=kafka'
Once it is not used, you can also delete the Kubernetes namespace:
kubectl delete namespace kafka