The closest Hank has ever shown to a moment of weakness was in Madness Combat 7 - Hank was willing to accept death rather than be constantly revived only to be painfully tortured to death by Tricky over and over again. He then spends most of said episode running away from Tricky, the first time we ever see him do so. Hank also seems to have a possible tiny tinge of mercy, as in Madness Combat 2: Redeemer he spares a grunt’s life by knocking him out instead of shooting him when he gave him information on the Sheriff’s location, though other reasons could explain this such as conserving ammunition. However, given the series’ fine line between what counts as unconscious and what counts as a kill when it comes to blunt weapons and hand to hand, this could’ve been intended as a kill, and given Hank’s total lack of mercy for anyone throughout the entire rest of the canon series this is very likely.
If this was an act of mercy and he did simply knock the grunt out, it was a one off event and after the events of Redeemer any ounce of mercy or humanity that Hank had left was gone.
