If you wish to rewind the master branch of the repository to a previous pushed commit, simply run this command — of course, with the appropriate commit hash:

git reset --hard a0b1c2d3e4f5g6h7i8j9k0l1m2n3o4p5q6r7s8t9
git push --force

This may have unintended consequences if, for instance, there are collaborators on your repository. But, I am sure you know what you're doing 😉

Undo a commit & redo

$ git commit -m "Something terribly misguided" # (0: Your Accident)
$ git reset HEAD~                              # (1)
# === If you just want to undo the commit, stop here! ===
[ edit files as necessary ]                    # (2)
$ git add .                                    # (3)
$ git commit -c ORIG_HEAD                      # (4)

1. git reset is the command responsible for the undo. It will undo your last commit while leaving your working tree (the state of your files on disk) untouched. You'll need to add them again before you can commit them again.
2. Make corrections to working tree files.
3. git add anything that you want to include in your new commit.
4. Commit the changes, reusing the old commit message. reset copied the old head to .git/ORIG_HEAD; commit with -c ORIG_HEAD will open an editor, which initially contains the log message from the old commit and allows you to edit it. If you do not need to edit the message, you could use the -C option.

Alternatively, to edit the previous commit (or just its commit message), commit --amend will add changes within the current index to the previous commit.

To remove (not revert) a commit that has been pushed to the server, rewriting history with git push origin main --force[-with-lease] is necessary. It's almost always a bad idea to use --force; prefer --force-with-lease instead, and as noted in the git manual:

You should understand the implications of rewriting history if you amend a commit that has already been published.

Further Reading

You can use git reflog to determine the SHA-1 for the commit to which you wish to revert. Once you have this value, use the sequence of commands as explained above.

HEAD~ is the same as HEAD~1. The article What is the HEAD in git? is helpful if you want to uncommit multiple commits.

hello! to revert a commit in a GitHub repository all you have to do is,

i. identify the commit to revert: find the commit hash of the commit you want to revert. you can do this by viewing the commit history either on GitHub or locally.

ii. revert the commit using the GitHub interface: on the GitHub repository page, click on the "Commits" tab and find the commit you want to revert. click on the commit to view its details and then click the "Revert" button. this will create a new commit that undoes the changes introduced by the selected commit.

iii. revert the commit locally and push the changes: if you prefer to revert the commit locally you can use git commands. first checkout the branch where the commit exists. then use the command git revert to create a new commit that undoes the changes. and finally push the changes to the repository.

iv. push the changes: if you reverted the commit locally, don't forget to push the changes to the GitHub repository.

if there's anything else you want to know and clarify let me know. : )

No, that feature isn't directly available on the GitHub web interface (as opposed to the "Revert" button recently added for GitHub for Mac/Windows)

Actually, it is for pull requests only, since June 24th, 2014:

Introducing the Revert Button

you can easily revert a pull request on GitHub by clicking Revert:

You'll be prompted to create a new pull request with the reverted changes:

git revert is a bit more complex to manage through the web as it can accept a range of commits.
It shouldn't be an issue in terms of collaboration though: a revert adds a new commit, it doesn't change the history of existing commits.

Just use this command in your terminal:

git reset --soft HEAD~1 

NOTES:
--soft keeps your changes staged (ready to commit again).
HEAD~1 means “the last commit.” and HEAD~2 means the commit before the last one