You can revoke permissions from individuals for any of your surveys.

From the “Design” tab within a survey, click “Survey Permissions”.

Hover your mouse over the small box to the left of the name of the person you wish to remove. The box will turn orange with a white “x” in the middle – click this orange box

Once complete, click “Save”

You will then see a “permissions updated” banner

More information about survey sharing can be found here; https://www.onlinesurveys.ac.uk/help-support/sharing-a-survey-with-another-user/