Yeah I wouldn't call headshots painful - matter a fact, to me it seems the harder the shot, the less it hurts lol. A good stinging jab could be described as "painful" to a certain degree, but a good right hand or left hook is generally not painful at all.
Bodyshots, those hurt. Those are PAINFUL. A good liver shot that freezes your body up is one of the worst feelings in boxing. Seeing these wars on TV, it blows my mind how these guys bodies still operate after being dug for 12 rounds.
Boxed this real heavy handed mf one time, very strong kid had many knockouts in the gym (true, asleep for 10-20 seconds before moving knockouts), and a ton of knockouts in amateur fights. His punches felt like being poked in the face with a sledge hammer, not painful at all just numbing. trying to catch his jab actually gave a similar feeling as his own glove hitting me - it would push my parry hand back into my mouth and cause the same numbing effect. Crazy power.