MySQL slave not able to execute long running update query
You need to stop replication, make the Slave have the same specs as the Master, then start replication.

Make sure the Slave has no incoming connections. Otherwise, that will make the SQL thread on the Slave compete with incoming connections that are running SELECT queries against the same table you are running DELETE.

If you cannot reroute the incoming connections, you will have to rerun the DELETE in chunks (perhaps 5000 rows at a time) on the Slave locally.

As a last resort, rebuild the Slave (after scaling up the Slave's hardware and configs).