Expanding what I wrote in a comment

The general rule is that you should not rewrite (change) history that you have published, because somebody might have based their work on it. If you rewrite (change) history, you would make problems with merging their changes and with updating for them.

So the solution is to create a new commit which reverts changes that you want to get rid of. You can do this using git revert command.

You have the following situation:

A <-- B  <-- C <-- D                                  <-- master <-- HEAD

(arrows here refers to the direction of the pointer: the "parent" reference in the case of commits, the top commit in the case of branch head (branch ref), and the name of branch in the case of HEAD reference).

What you need to create is the following:

A <-- B  <-- C <-- D <-- [(BCD)-1]                   <-- master <-- HEAD

where [(BCD)^-1] means the commit that reverts changes in commits B, C, D. Mathematics tells us that (BCD)^-1 = D^-1 C^-1 B^-1, so you can get the required situation using the following commands:

$ git revert --no-commit D
$ git revert --no-commit C
$ git revert --no-commit B
$ git commit -m "the commit message for all of them"

Works for everything except merge commits.

Alternate solution would be to checkout contents of commit A, and commit this state. Also works with merge commits. Added files will not be deleted, however. If you have any local changes git stash them first:

$ git checkout -f A -- . # checkout that revision over the top of local files
$ git commit -a

Then you would have the following situation:

A <-- B  <-- C <-- D <-- A'                       <-- master <-- HEAD

The commit A' has the same contents as commit A, but is a different commit (commit message, parents, commit date).

Alternate solution by Jeff Ferland, modified by Charles Bailey builds upon the same idea, but uses git reset. Here it is slightly modified, this way WORKS FOR EVERYTHING:

$ git reset --hard A
$ git reset --soft D # (or ORIG_HEAD or @{1} [previous location of HEAD]), all of which are D
$ git commit

In general, you can go back to a commit in your history with git reset.

This is not possible with GitHub Desktop. GitHub Desktop is more of a tool to synchronize your repositories and not a full featured GUI client.
But that doesn't mean you have to use the command line, since there are alternatives. You can find a list here. To mention a few (that support git reset):

• TortoiseGit (Windows)
• SourceTree (Mac, Windows)

Here is how you do it on command line. Most clients provide this in their UI using the same vocabulary (usually, you are able to select a commit and reset to it via context menu).

You will go back to the previous commit with

git reset HEAD^

or some more commits (for example 3) by

git reset HEAD^3

or to a specific commit by

git reset f7823ab

Have in mind that, by default, the option --mixed is passed to git reset. So, all changes made, since that commit you reset to, will still be there.

To get the original state of the commit that you want to 'revert', you have to pass --hard. For example:

git reset f7823ab --hard