Requirements OldTwitter
Direct install for Firefox, Chrome, Edge
You need to install the OldTwitter extension for this to work. Once installed, head to your twitter profile.
Open the developer console -> CTRL + SHIFT + I
Paste the Like deleter or Retweet deleter into the console
Make sure to change the @USERNAME to the username (case sensitive) of the account you wish to delete from your likes/retweets page.
Example: Changing the username to @elonmusk - will delete all the posts you have liked/retweeted from @elonmusk