Sometimes, they can be repaired. See http://www.bobvila.com/articles/retaining-wall-repair/#.VzE8w9Lrvjo

You must rebuild the wall. Add drainage behind the new wall to relieve hydrostatic pressure (water stuck behind the wall). Drain it to daylight!

How tall is it?

Here in California wall that lean can often be repaired or at least supported. Oftentimes after a quake or as a preemptive supports can be put up on either side. They are made of the the same blocks of the wall. If you need a photo I can post one.