Just cause someone looks like he can not fight does not mean he is unable. Dirty fighters know how to hit people where it counts and when they least expect it. When you corner a person like that you never know what is in store for you. Much like a rogue a dirty fighter takes advantage of people every chance they can. With no regard for what is socially acceptable they work every angle to achieve their goals. Thinking outside the box is what they do best and when they get friends that accept their ways they are loyal to them unlike anything else.
Low Blow (Ex): Starting at 5th level a dirty fighter learns to hit foes where it counts. When a dirty fighter hits a foe that is flat-footed double the damage of his attack. Should a dirty fighter score a critical hit with this attack, the extra damage is not multiplied. Ranged attacks can count as a low blow only within 20 feet. Also any object thrown by the dirty fighter retains the enhancement bonus from his Iron Fist ability and does lethal damage.
Sucker Punch (Ex): Starting at 10th level a dirty fighter knows just what to do to catch his foe off guard. The first attack on a foe is always flat-footed. This ability will not effect a foe a second time ever. Also he can make a Bluff check to feint in combat as a swift action once per round.
Discomfort (Ex): Starting at 16th level a dirty fighter can use his surroundings to make it hard for his foes to move. Treat all adjacent squares to the dirty fighter as difficult terrain.
Sicken (Ex): Starting at 20th level a dirty fighter's low blow has a chance of nauseating his foe when he hits them flat-footed. If you hit a flat-footed foe and it fails a Fortitude save (DC = 10 + half your pugilist level + Wisdom modifier) it becomes nauseated for 1d4 rounds. This effect happens only once per round and does not stack but it can overlap increasing number of rounds.