People naturally think that more = better. With a handicap this is reversed with less = better, which is unintuitive to most people. Also it is a word mostly used in golf, so if your customers don't play or understand golf, you will have a problem.
Assuming that you want fewer errors here, you then want the person with the fewest errors to have the highest score.
Why not start out by giving everyone say 100 points, and then deducting 1 point for each error (or more for major errors). In the end you will have a points table with the highest at the top and lowest at the bottom.
Someone who would have had a handicap of 15 in your system would now have a score of 85. "Hey, 85 isn't so bad, I'll bet that I can get to 90" is more likely than "I had a handicap of 15 maybe I can get it to 10"
To summarise: Give everyone equal points and deduct points for errors. Then you can just use points as your measure.