A strong wall features base material that is well-compacted, compacted material in front of the wall that will prevent kick-out, and stepped-back materials. A poorly built wall is a wall that has an uneven base with no compacted material in front of it and no step-back to the materials will eventually lean, separate or even topple.
Proper thought and effective design plans are important before you start digging in the ground.
You should also take water into consideration as it can weaken and destroy retaining walls several ways. It can do this by washing away the base material that supports the wall. It can also cause issues saturating the soil behind the wall and then applying incredible pressure. This is what causes walls to start to lean, bulge and eventually topple. Properly-built walls will be constructed and graded correctly to make sure water does not get behind it and will have a proper drainage method to immediately get rid of any excess moisture.
