Just delete the contributor.
The Payment table was set up for its records to be deleted when the contributor is deleted.
A list of past members and donors is worth keeping (even though a record of their contributions will be deleted).
You will need that handy text file containing common SQL commands. Open it alongside your phpMyAdmin window.
1. In phpMyAdmin, search for the contributor. Examples: Mrs July, Mr February.
Amend then copy the required command from the handy SQL file.
2. Identify the correct ID of the contributor and enter this in the command (in that handy text file).
The ID of Mrs July is 8.
(The command at the top is altered to become the command at the bottom).
Copy the bottom command into the SQL text box, the click Go.
Result - first:
Browse PastContributor table to check if you wish.
Use the handy text file for the correct command and amend to use the correct ID.
Copy the amended command (the lower one) into the SQL text box and click Go.
You will be asked to confirm the deletion.
Click OK and the delete takes place - irreversibly!
If you examine the Payment table, you should see payments for ID=8 have also been deleted.