Look for someone with a very low SR average
Those victory leaderboards on jason's site where depressing when you looked at the profiles of the front runners. I still have a lot of victories, 7.2% win percentage, and most of those were not at SR 99. If matchmaking worked correctly and I qualified, my win percentage doing race B and C can't realistically be higher than 5.6%.
An interesting stat would be looking at victory percentage vs avg SR.
I hope GT7 will split out victories. A victory in D/E should not count the same as a victory in a A+/S room. At least not while DR resets remain. It's too easy to manipulate DR/SR to get easy victories.
Since I have been resetting my stats every day for GT7 (Sticking to 1/1 at 'save' time) I have had more victories from the back on race C. Interesting note is that SR.B is the easiest to get a victory in from the back, slowest match ups. At lower SR there is guaranteed a fast DR reset on pole farming victories. At higher SR the back becomes slower while the front runs away. But there's always that broken 80-89 SR room that puts the fastest 80-89 SR drivers against the slowest 90-99 SR drivers.
Getting tons of victories in this game is all about when (what time) to race and in what SR range to race :/
Here's a notorious one with 35% win percentage...
https://www.kudosprime.com/gts/stats.php?profile=1194725