What you want to do is discard part of the work previously made and already pushed to the remote. This means modifying repository history, and it's almost always a bad idea, for at least two reason:
- You are discarding work already done, and may not be able to recovery it. Even if it was wrong you can still keep track of it and simply go ahead with a new commit that discard the differences.
- If someone else apart you is working on the repository he will no longer be able to push to it, since the history of the remote and their local won't match. They will have to clone again the repository and add their work manually, merging with diff tools.
If you really want to change the history of the remote repository, matching it with your local repository, you can simply do a force push:
git push --force
Anyway, as others already pointed out in the comments this might be a really bad idea.