Cannot uninstall Language Pack 0 because it is not deployed

If you have this error, it means you are trying to uninstall a solution which is not installed (deployed).

So,
First check Central Administration - System Settings - Manage Farm Solutions - Check if your solution is deployed. If it is not, deploy it.

If you have trouble by deploying it, try to remove the solution. (Yeah, skip uninstall phase)

Removing solution PowerShell cmd:
Remove-SPSolution -Identity solution.wsp -Force
Removing solution stsadm cmd:
stsadm -o deletesolution -name solution.wsp -override

Add Solution PowerShell cmd:
Add-SPSolution D:\solution.wsp
Add Solution stsadm cmd:
stsadm.exe -o addsolution -filename D:\solution.wsp

Install Solution PowerShell cmd:
Install-SPSolution –Identity solution.wsp -GACDeployment -Force
Install Solution stsadm cmd:
stsadm -o deploysolution -name solution.wsp -immediate -allowCasPolicies -force -allowGacDeployment