The Book

To obtain a list of installed patches you can do:

wmic qfe list

To uninstall a listed patch, you do:

wusa /uninstall /kb:<kbnumber>

Here are some links with more information:
http://www.systemcentercentral.com/BlogDetails/tabid/143/indexid/57960/Default.aspx
http://support.microsoft.com/kb/934307
http://technet.microsoft.com/en-us/library/dd883262(WS.10).aspx

Note: the 934307 KB article says that you can't use /uninstall on Windows 2008 - this does not apply to Windows 2008 R2 - they enabled the uninstall switch on R2 (see the last link).

And to do it from a remote computer :

wmic /node:SRVNAME process call create "powershell wusa /uninstall /kb:2844286 /quiet /norestart"

and to have more information on parameters

wusa /?