The details of this movie are specially fuzzy on my mind.
I saw it at some point in the 80s I think and I can only remember very vague facts.
Main character has immunity to harm. I “think” is more like super fast healing, à la Wolverine.
At one point in the movie he has to go from one place to another and there’s a remark in the sense since he doesn’t fatigue, he’ll be able to run at peak human velocity all the way and hence make it in time. I seem to recall he runs through a forest and it is elated to save his son.
There’s a girl, some kind of scientist that’s helping him but I don’t think it was the mother.
The main character has a son. In his early teens.
At the end of the movie, this is the scene I remember more vividly, the son wants to know if he’s inherited the healing powers of his dad, so he purposely cuts himself on the hand washing on the kitchen sink. The main character comes running to find him holding the hand under water and he confesses what he has done and why. When he shows the hand, the injury is gone, implying he does, indeed, share his dad’s ability.