Unfortunately, there is no option to bulk delete comments from your history. If you want to get rid of everything you've ever said on this platform, you will either need to continue doing this to each and every one of your comments or opt for a different approach and make some changes to your channel.
To delete all the comments in one go, you can hide your channel temporarily which will delete all your comments and replies in the process. Once deleted, you can activate your channel again and your deleted comments will not be restored.
but if you dont want to delete or hide your channel you can do it with the help of this extension, you can delete all your comments on youtube without having to bother with manual clicks one by one. this script will do it, you just press the start button and you can let the computer work for you.
How to use and Demo : https://www.youtube.com/watch?v=KGm2qnL-ObU
I really hope for your support by subscribing to my youtube channel : https://www.youtube.com/channel/UCqRqvw9n7Lrh79x3dRDOkDg
note: The extension may not work in the future if myactivity google changes their layout, in this case, you should subscribe to my channel to get an update for the new script.