How realistic is it to be completely "fair and impartial "?

SGT Aldana, all I can tell you is to keep trying to solve the puzzle. The solution that works best for me, probably wont work as well for you. The underlying formula that runs through all of these responses should only be used as the foundation for your trial and error. It's the individual person variable that prevents the "one size fits all" answer. You'll get it so long as you don't give up.

I go out on that limb up to a point. I can't afford to devote so much time to one Soldier, NCO or Drill Sergeant that the rest of the unit suffers. Experience tells me that cruel as it is, you might be doing that Soldier, NCO or Drill Sergeant a favor by recommending a change of scenery - as in out of the Army and into the civilian world.

Every Soldier deserves the attention and diligence of their NCO. I preach this; I practice it. Not every Soldier is cut out to be the next Sergeant Major of the Army, but one of them is. Is it one of your Soldiers right now?
How will he/she view your leadership down the road when they have Soldiers?
Are you a leader they will respect enough to use your techniques someday when they have Soldiers?

Some of your Soldiers, right now are not cut out for the military service. They will do their best - or not - but it is the job of the NCO to get the most out of each and every member of the team. You never know when you'll have to deploy and you will have to relay on your "needy" Soldier with your life.
Train them and motivate them like your life depends on it. It just might.
When they fall short of the standard, it is our job to motivate them. If you can't do that or they really are a lost cause, support them through the transition process. You never know when that Private becomes a boss someday.
The biggest compliment I ever got was from a Soldier who had been out for years, calling me out of the blue to ask for a reference. He had very kind things to say to me about how big an influence I was on him. I wasn't easy on him by any means, but he RESPECTED me.
You will never win them all; sometimes the Army gives you snake eyes. But do your best when you have the awesome responsibility to lead. It will come back to you someday.

based on what you wrote.. i do the same thing... but at the same time... those soldiers that our stagnat sometimes need that push from a NCO to push their drive...

It is possible (and desirable) to impartially reward superior performance and correct poor performance regardless of race, creed, ethnic origin, etc.