"It's an incredible feeling having finally won in a Lions Test," said Williams, who featured in the second and third Test defeats to the All Blacks in New Zealand four years ago, as well as last week's heartbreaking reverse to the Springboks in Pretoria.
"I am really proud to have been a part of this team and it's just a shame we lost the series 2-1.
"It's my first win over the Springboks in nine attempts and my last game for the Lions."
Voted IRB World Player of the Year in 2008, Williams had been seen by many as a certainty for the Lions Test team nine months before departure for South Africa, yet an indifferent season back home and a lack of tries once the Lions arrived in South Africa had seen him miss out on selection for the first international before coming on as a second-half replacement in the second.
Wales' record try scorer, Williams had been heavily criticized in certain quarters as critics expected him to repeat his sublime form of a year ago, yet the 32-year-old never let the negative attention affect him as he continued to work hard when ever he wore a Lions shirt in the Republic.
Now, just under six weeks after arriving in South Africa, Williams was finally able to claim his reward for his patience and positivity as he supplied two poacher's finishes to fine breaks from Jamie Heaslip and Riki Flutey. It was clearly a satisfying moment for the popular Welshman.
"It's a great way to show people who felt I wasn't good enough. I know I've been good enough from the start," added Williams.
"I was just glad I got the chance to play. I was rubbing my hands with glee when I was named in the starting line-up.
"I came off the field shattered, but it was a game I really enjoyed. I didn't force things and got the ball in my hands. I went out to enjoy myself and that's exactly what I did. I worked my socks off and at half-time I was looking for a set of new lungs.
"I wanted to go out with a bang in my last chance in a Lions jersey. I know I haven't been playing to my potential and the frustrating thing is that after this game I know what I've been doing wrong."