In earlier versions(Microsoft Visual Source Safe) you can achieve this by logging in from the Admin account and undo other's changes as the Admin. But the Visual Studio Team Foundation Server, you don't have the GUI to achieve this. So you'll have to use the Visual Studio Command Prompt.
You just have to do is Open the Visual Studio Command Prompt (no need to log in to the Team Foundation Server), and provide the relevant command. You have to specify few parameters to the command and they are;
- Operation needs to be done (e.g:- undo, check out, etc...)
- Work space and the user name of the user who has checked out the item.
- Location/path of the item which in being checked out.
Herewith I have attached a screenshot of the command in my case.