Locate broken package dependencies

I have been cleaning up my system over the past month removing packages that I installed specifically for school and other purposes. Now that I no longer needed these packages I have uninstalled them I would like to check my system for package dependencies that may still be installed. How to I check my system for these files?

perhaps zypper verify ?
also useful for cleanup: zypper packages --unneeded ; zypper packages --orphaned

The

zypper --needed

is the command I was looking for, I had searched the zypper man page and looked right over it. Thank you.