It wasn’t a padlock on a chain. It was a “U” styled hard lock. He grabbed it on the part opposite the lock and used the locking cylinder as the impact point.
It is essentially a hammer at that point.
I think you’re referring to the padlock “shank” or “shackle”. So in other words this guy was swinging a padlock by it’s shank. One could easily die with a padlock to the head when swung by it’s shank or chain. In fact, one could die simply by being hit in the head by a thrown padlock. And it wouldn’t be the first time.
I’m calling this guy a trained assassin.
Even if self trained, he is practiced, stealthy, quick and accurate, like the viper he is.