If your rendering is under- or overexposed, this may be caused by:
1. Wrong exposure value
To fix this, depending on your workflow, adjust exposure in
- The Post tab of the Corona VFB
- The camera you are rendering from
- Render Setup > Camera > Edit Tone Mapping...
See also: How to use photographic exposure controls?
2. Wrong lighting
Make sure you are using correct light units and intensities and that your lights are facing the right direction.
See also: What light units does Corona use?
3. Wrong materials
Make sure your materials are not too bright or too dark.