I have an idea to make a twitter bot that block annoying accounts:
my question is can I block accounts on behalf of other user?
I am using  tweepy
I already have tokens for my account
Yes, if you have access tokens for the other user. You can get these by using the sign-in with Twitter API, and have the other user go through that process to authorize your app.
how to block twitter accounts on behalf of others with tweepy?