If you have committed files that you shouldn’t have (e.g. passwords) you can use the following to delete the last commit provided the commit has not been pushed.
git reset --hard HEAD~1
HEAD~1 means the pervious commit, you can also use the SHA-1 of a commit to delete all commits back to that commit.
--hardgets rid of any changes from the selected commit(s). Use
--softto leave the files as
changes to be committed.
If you have pushed the commit then you can either do
git revert HEAD
which creates a new commit that revert changes in the last commit but the data is still present in the history of the repository.
Even if you tried to do
git push --force after you deleted the commit from your copy the data will exist in people locals copies until they pull the latest changes. This also makes merging a lot more difficult.