It seems like you might be referring to a comparison between two waves in a diagram, likely comparing their amplitude, wavelength, or frequency. Based on the context you've provided, if the bottom wave is being compared to the top wave in terms of its height or strength, you might be looking for "amplitude."
Therefore, you could complete the statement as follows:
"The bottom wave has a greater amplitude."
If you meant to compare a different aspect, please provide more context so I can assist you better!