Harry Bennett confronted the 70-year-old in Hastings town centre over claims of an incident involving his friends.
The 20-year-old, who was drunk and had also been taking steroids, targeted Steven Murray as he walked home past Priory Meadow.
Video footage showed Bennett punching him in the face, knocking him to the floor.
He then rained down nine more blows as the pensioner lay prone on the floor.
Then, with Mr Murray clearly unconscious, Bennett took a run-up and kicked him in the head.
Mr Murray was left with blood in his hair, broken ribs, jaw and tooth damage and bruises.