How to revert last commit and remove it from history?
First off, git revert is the wrong command here. That creates a new commit that reverts an older one. That's not what you're asking for. Secondly, it looks like you want to revert HEAD instead of HEAD^.
If you haven't pushed this anywhere, you can use git reset --hard HEAD^ to throw away the latest commit (this also throws away any uncommitted changes, so be sure you don't have any you want to save). Assuming you're ok with the sensitive information being present in your copy and nobody else's, you're done. You can continue to work and a subsequent git push won't push your bad commit.
If that's not a safe assumption (though if not I'd love to hear why), then you need to expire your reflogs and force a garbage collection that collects all outstanding objects right now. You can do that with
git reflog expire --expire=now --expire-unreachable=now --all
git gc --prune=now
though this should only be done if you really absolutely need to do it.
If you have pushed your commit, then you're pretty much out of luck. You can do a force-push to revert it remotely (though only if the remote side allows that), but you can't delete the commit itself from the remote side's database, so anyone who has access to that repository can find it if they know what to look for.
If you don't care about the commit, just do:
git reset --hard HEAD~
to blow away the commit.
If you want the changes to be in working directory, do:
git reset HEAD~
Depending on what you have done with git revert, you might have to change the above commands. Revert creates a new commit that reverts the commit you wanted to revert. So there will be two commits. You might have to do HEAD~2 to remove them both.
Note that, usually, revert is the safer way to, well, revert changes. But here, since you want to remove sensitive data, reset is the best approach.