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

Reinstall a WSP Package in Sharepoint 2010

Steps:
1. Retract
2. Delete Solution
3. Add Solution
4.Deploy Solution

1.Retract:
Go To Central Admin - System Settings - Manage Farm Solutions - Select and Retract the solution

2.Delete Solution:
Open PowerShell as Admin
Type
Remove-SPSolution –Identity YOUR_WSP_NAME.wsp

3.Add Solution:
Open 14 hive in cmd
C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14
Run command:
stsadm.exe -o addsolution -filename D:\YOUR_WSP_NAME.wsp

4. Deploy Solution:
Go To Central Admin - System Settings - Manage Farm Solutions - Select and Deploy solution