William Zabka was 17 in The Karate Kid when he played the character 'Johnny Lawrence'.
That was over 40 years ago in 1984.
This was his first recorded movie acting credit (although may not technically be his first actual acting role).
Today he is 58, and has starred in 34 movies in total, 34 of those since The Karate Kid was released.
In The Karate Kid, I think William Zabka looks: