This sounds kind of stupid, but can a grounded fig make an attack if he moves into hindering as his last square? The move into hindering ends his turn doesn't it? I'm pretty sure that's how it is, but I want confirmation.

Thanks

First, I assume by "grounded" you really mean "non-flier", as a grounded flying character (yes, they are indeed grounded when they are on the ground and not elevated or soaring) would ignore the hindering terrain while moving. Pet peeve of mine; people have been misusing this term a lot lately

Second, the attack from Running Shot (or Charge, for that matter) comes after the movement; you don't get to keep moving after the attack is made like you do with, say, HSS option 1. Since your movement is already over anyway before you attack, stopping because your character enters hindering terrain does not prevent the attack in any way at all.