The Dexterity stat affects how well you fare in combat, and for the most part it has to do with how often you hit your opponent. This, in combination with the characters strength, ultimately decides the hack'n slash outcome of a fight.

3 dex fight

With only 3 dex this character has a hard time landing any hits.

10 dex fight

But with 10 dex the chances of hitting the pesky rat increases noticably.