Sharepoint - Retract/Remove Solution - SharePoint 2010
Central Admin - System Settings - Manage Farm Solutions, pick your wsp and hit Retract, then Remove once it's done.
Using STSADM
Open command prompt and navigate to
C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\BIN
Use the stsadm command
stsadm -o retractsolution -name solutionName.wsp -immediate
and then remove the wsp
stsadm -o deletesolution -name solutionName.wsp
Using Powershell
Go to All Programs => Microsoft SharePoint 2010 Products =>SharePoint 2010 Management Shell =>Run as administrator
Uninstall-SPSolution -identity "solutionName.wsp"
Remove-SPSolution -identity "solutionName.wsp"