According to sharkscope, the best player on PO, lilturkgirl, is -$40 total profit. Interesting that the best player is actually net negative. Check out the stats for yourself here:
SharkScope - Online and Live Poker Statistics
If you need a worse player to compare them to, here is d33p5t4ck3d from PO's stats. Over 350 games + $1832 with a 72% ROI. Much worse than lilturkgirls stellar results.
SharkScope - Online and Live Poker Statistics
Here's Lilturkgirls graph over 800 tournies:
Attachment 1335
For a net negative player, she sure is the best!