Grant, for all his genius had some world class goofs to his name.
I doubt that he could be classified a genius but, he certainly was ruthless.
I have read several books about Grant as well as his own well-written memoirs, and while he was definitely ruthless in pursuit of the success of a mission, he was in no way heartless.
He and General Patton had that in common in my opinion, they believed that when an enemy was weakening or on the run, to keep up the pressure with less consideration of the toll on their own troops because they thought in the end, it would result in the lowest total loss of life and greatest tactical success.
But they both did understand the toll it took on their own troops, they simply thought it was the best approach in the long run.
And if not ruthless, at least tenacious. It was his dogged persistence, not any tactical brilliance, that won for the Union.
Where's the dividing line between the two?