UEFA EURO 2008
48 Achievements
1,000
Xbox 360
Biggest Win
In UEFA EURO 2008™ mode beat the biggest win of Germany 13 San Marino 0 (solo only)
25
How to unlock the Biggest Win achievement in UEFA EURO 2008 - Definitive Guide
Start up UEFA EURO 2008 mode and play on Amateur with 20 min halves. Play the finals only. Spain is a good team to use. Just rack up a 14 goal lead and run out the rest of the time. Probably a good idea to get a 15-16 goal lead just in case the CPU score a couple on you. The achievement will unlock at the end of the game.
I would go for this when doing the achievement above. You can win 15-1 or 30-10 you just have to win by more than 13 goals, and by going for this when doing the achievement above all the settings such as a 20 minute match will favour your odds of scoring this many goals.