Yes — this effect can be done with a single softbox placed slightly behind the subject so only the edge of the face/body catches the light. If your setup is correct but the subject isn’t going dark enough, the most likely issue is exposure.

Try reducing exposure by about 1 to 2 stops (for example, use exposure compensation of -1 or -2 if your mode allows it). That will help keep the subject mostly black while preserving the rim light.

For a true silhouette with rim light, the key is:

• light positioned just behind the subject from camera view
• subject turned in profile toward the light
• exposure lowered enough that the unlit side falls to black

If you want a slight bit of detail on the cheek facing the camera, move the subject a little back toward the light until just a touch of light appears.

An umbrella/continuous-light setup may work similarly if you can place it in the same position, but the provided answers mainly support the one-softbox method.