Hello, one player in my server made claims in a way that can be considered griefing.

Removing them one by one can an option but is quite painful. I wonder if there is a way to remove those claims easier way.

Why one by one? Do you know you can select an area by dragging the right click on the world map?
The only way to delete all claims of a player in 1 action is to remove their claim file in the world data. That requires stopping the server though. It's probably easier to remove them normally.

yes I am aware that I can drag multiple chunks and bulk claim/unclaim them. However in my case, the player (griefer) claimed his/her chunk around other players' claims all around the overworld.

The only way to delete all claims of a player in 1 action is to remove their claim file in the world data.

This can be my solution! Thank you for the advice!