YouTube?

This is limited in the Google account. At the time of this answer, it works as follows:

• go to myactivity.google.com and there to manage YouTube history –>
• above on the tab “Interactions”
• choose “Likes and Dislikes for Videos”
• top of the three points and “Delete all”

In channel subscriptions it is not possible at the time of the answer to delete all at once. To do this, you would have to delete the entire YouTube history, which is the same for a new account.