I will not give you the most common answers like (VPIP, PFR or 3-Bet, for example)... I'll give you a very specific, but useful, stat that I used to have on H2N4 when I was using it:
"Fold percentage on bet on turn after calling a check-raise on flop".
I don't know if you can create this with every poker tracker, but Hand2Note has this feature.
Anyway, the idea of creating this state is to know how passive and submissive a weak player is against check-raise; most part of the weak players fear this more than they should and insta pay the raise just by pride and/or to try to not look like he is afraid and with a weak hand to the opponent (in this case: you).
If you have this stat with you, you may be able to know if this player usually surrender after being stressed by a check-raise and this will make you get way more chips than you would if you didn't know this info about him...
The bad part of this is that you will need to play a lot of
hands until you reach this situation enough times against each player.