Yes, I agree with you that he is powerful and by the end of Legion, Velen clearly showed that he can be aggressive if needed. I was just pointing out that he likely didn't use his power in that KJ's death cinematic, or it would have contradicted with what he said shortly afterwards (that in KJ final moment, he learned to let go of the past for both himself and his son). Wouldn't make a good case of letting go of the past if you give an already-dying guy a kick so he dies faster