If you want to delete for example the last 3 commits, run the following command to remove the changes from the file system (working tree) and commit history (index) on your local branch:
git reset --hard HEAD~3
Then run the following command (on your local machine) to force the remote branch to rewrite its history:
git push --force
Congratulations! All DONE!
Some notes:
You can retrieve the desired commit id by running
git log
Then you can replace HEAD~N with <desired-commit-id> like this:
git reset --hard <desired-commit-id>
If you want to keep changes on file system and just modify index (commit history), use --soft flag like git reset --soft HEAD~3. Then you have chance to check your latest changes and keep or drop all or parts of them. In the latter case runnig git status shows the files changed since <desired-commit-id>. If you use --hard option, git status will tell you that your local branch is exactly the same as the remote one. If you don't use --hard nor --soft, the default mode is used that is --mixed. In this mode, git help reset says:
Resets the index but not the working tree (i.e., the changed files are preserved but not marked for commit) and reports what has not been updated.