As in, who is the worst actual professional wrestler? Somebody who actively sought out a career in professional wrestling, from the get go and didn't just fall into it (ex: someone who always wanted to wrestle, didn't have a day job, etc)? Someone who made it through wrestling school, and into a well known promotion, but were just so bad at it? Someone who never realised that wrestling "wasn't for them" and continued to stick around in the business?
With these kinds of criteria we can exclude the likes of:
The Great Khali (acting background)
Kurrgan (was just passing through on the way to an acting career)