Unexpected error on server associating the workflow

Some of us might be faced this issue while publishing the workflow from SharePoint designer. To resolve this, need to extend the UserDefinedWorkflowMaximumComplexity limit for the web application.

Run the following script in your farm

[System.Reflection.Assembly]::LoadWithPartialName("Microsoft.SharePoint") 

$new_limit = 10000;

$web = Get-SPWebApplication "your web application URL"

$web.UserDefinedWorkflowMaximumComplexity = $new_limit 


$web.Update()