Strength

From the KF manual

The stronger you are, the more damage you can inflict on your opponent.

What's the use?

Per point of strength you get X points of additional damage. (Unfortunately, there is a formula behind it, which you can't see at first sight)

Example: If you have 20 points of strength, you get a bonus of 2.7 on your base damage. The basic damage (by weapon) from 6.0 to 12.0 increases to 8.7 to 14.7