Termination
In order to dismiss an employee fairly and (in respect of those with more than one year's continuous employment) avoid liability for unfair dismissal, you will need to dismiss for one of the five statutory fair reasons (redundancy, lack of capability or qualifications, misconduct, breach of a statutory duty or some other substantial reason - "SOSR").
Whilst it is not always possible to avoid an employee bringing a claim, there are many steps you can take to minimise the risk of them doing so or, at the very least, reduce the level of any award made by a Tribunal.