Delete failed pipelineruns:
kubectl -n target-namespace delete pipelinerun $(kubectl -n target-namespace get pipelinerun -o jsonpath='{range .items[?(@.status.conditions[*].status=="False")]}{.metadata.name}{"\n"}{end}')
Delete successful pipelineruns:
kubectl -n target-namespace delete pipelinerun $(kubectl -n target-namespace get pipelinerun -o jsonpath='{range .items[?(@.status.conditions[*].status=="True")]}{.metadata.name}{"\n"}{end}')