Take note in my combat system, there is no such thing as "pummeling damage." All damage described on this page refers to normal combat damage, applying to any attack that reduces a combatant's hit points.
Pummeling describes attacking with the fist, an action that can be performed in lieu of a weapon or as a secondary weapon. Unlike a normal weapon attack, pummeling costs only 1 action point from a combatant's movement. Note that this cost is not reduced when a combatant receives more than one weapon attack per round.
The amount of damage caused by pummeling is equal to 1d4 minus 3, or -2 to 0 hit points (with all damage less than zero equalling zero). When pummeling, the combatant's strength bonus is added, so that a character with a strength bonus of +3 would cause 1-4 damage when pummeling.
When using a gauntletted fist, damage from pummeling is increased by +1.
Unlike damage done with other weapons, when rolling a 20 critical the total damage from pummeling is 2d4 -3, before adjustment (normal weapon adjustments cause the damage to be adjusted before doubling or tripling damage). A second natural 20 would alter the damage done with pummeling to 3d4 -3, with a d4 added to each additional natural 20 rolled.
When an attack with pummeling results in a fumble, the combatant should roll 2d6; a result of 'snake-eyes' will mean that the combatant will lose the use of that limb and will suffer an injury causing 1d4 points of injury.