If you face any issues in your SharePoint environment due to long running timer jobs, and if you want to kill them, issue the following PowerShell commands.
Get-SPTimerJob | where {$_.name -like "Name of your suspicious job"}
This command will give you the Timer Job ID.
$JobName = Get-SPTimerJob -ID
Get the Job Name from Timer Job ID
$JobName .Delete()
Delete the Timer Job.