The abortrescan RPC stops current wallet rescan triggered by an RPC call, e.g. by an importprivkey call.
abortrescan none
*bitcoin-cli help abortrescan
abortrescan Stops current wallet rescan triggered by an RPC call, e.g. by an importprivkey call. Note: Use "getwalletinfo" to query the scanning progress. Result: true|false (boolean) Whether the abort was successful Examples: Import a private key > bitcoin-cli importprivkey "mykey" Abort the running wallet rescan > bitcoin-cli abortrescan As a JSON-RPC call > curl --user myusername --data-binary '{"jsonrpc": "1.0", "id": "curltest", "method": "abortrescan", "params": []}' -H 'content-type: text/plain;' http://127.0.0.1:8332/