such as directly straight or directly diagonal.

I just rolled a knockback on a fig 1 square to my right and 5 squares to my front, and that isnt even straight diagonal or straight ahead and he is on a roof corner.

by the FAQs description, the attacker decides the direction of the KB, so can i command it to move directly left, off the roof? or does it have to "logically" be knocked backwards?

the wording of the FAQ quite gives the attacker enough power to determine KB directions on non-straight attacks.

thanks in advance!

Yeah, the FAQs are poorly worded on this. Technically, the attacker could 'knockback' the target towards the attacker if he wanted to, by the way the FAQ is worded.

However, most people I know would use logic to determine the direction (IE. the target must be moved away from the attacker in either a straight line or diagonal). In your example, that would be straight back or diagonally to the right (or even possibly straight right, depending how far you want to take it).

Don't worry about the FAQs.

Read the rulebook (current Universe):

"The attacker moves the target character AWAY from the attacking character along a straight line..."

So even if the FAQs say that the attacker can CHOOSE a straight or diagonal line, the rules still say "away" from the attacker. So there are only ever 3 choices you get: vertically "away", horizontally "away", or diagonally "away".