Ok... so stacking all the grappling feats I could on a wild child brawler.
I'm seeing a +34 grapple bonus at 20, [+41 to maintain if it doesn't break.] and up to 12d8+33 [45-129] damage per round maintaining grapple. (Rapid grapple chain) And a CMD of 47 for them to break out of it.
Outside ungrappleable things, how terrible is it?
Grappler Spec Human 16,16,16,7,12,10 (25pb) +2 Str
01: Improved Grapple, Deadly Grappler, Brawler's Cunning, Martial Flexibility, Martial Training, Unarmed Strike, Animal Companion
02: Brawler's Flurry (2WF)
03: Weapon Focus (Grapple), Maneuver Training (Grapple)
04: AC Bonus +1, Knockout 1/day, +1 WIS
05: Kraken Style, Wild Tricks, Brawler's Strike (magic), Hunter's Tricks
06: Martial Flexibility (Swift Action)
07: Greater Grapple, Maneuver Training 2 (Trip, Grapple 2)
08: Brawler's Flurry (Im2WF), +1 WIS
09: Rapid Grappler, AC Bonus +2, Brawler's Strike (cold iron and silver)
10: Martial Flexibility (Free Action), Knockout 2/day
11: Chokehold, Maneuver Training 3 (Disarm, Trip 2, Grapple 3)
12: Brawler's Strike (Alignment), Martial Flexibility (Immediate Action), +1STR
13: Kraken Throttle, AC Bonus +3
14:
15: Kraken Wrack, Brawler's Flurry (Gr2WF), Maneuver Training 4 (Bull Rush, Disarm 2, Trip 3, Grapple 4)
16: Awesome Blow, Knockout 3/day, +1STR
17: Grabbing Style, Brawler's Strike (Adamantine)
18: AC bonus +4
19: Body Shield, Maneuver Training 5 (Overrun, Bull Rush 2, Disarm 3, Trip 4, Grapple 5)
20: Improved Awesome Blow, Martial Flexibility (Any Number) +1INT