I did this when going for thumping achievement.
- choose an easy opponent in league
- take over management of easy team about to face
- team you want to beat only put in defenders and goalkeepers, defender in goal also, do this in team selection.
If your using team such as man city you should score lots of goals, put out your best team for the winning team. Attacking or very attacking in tactics.
- if you manage to hammer the other team with several different scorers, you will unlock this a few days after the match.