If penalties to damage bring the damage result below 1, a hit still deals 1 point of damage. When a combatant deals damage with a weapon in the combatant's off hand, a combatant add only one-half of the combatant's Strength bonus. When a combatant deals damage with a weapon that the combatant is wielding two-handed, the combatant adds one and one half times the combatant's Strength bonus. Light weapons don't get this higher Strength bonus when used two-handed. A Small combatant's unarmed strike deals 1d2 points of damage.
All damage is subdual damage.
Normal Damage A combatant can specify that it's unarmed strike will deal normal damage before it makes an attack roll, but the combatant suffers a -4 penalty on it's attack roll because it has to strike a particularly vulnerable spot to deal normal damage. When a combatant makes an attack roll and gets a natural 20, the combatant hits regardless of the target's AC, and the combatant has scored a threat. If the critical roll also results in a hit against the target's AC, the combatant's original hit is a critical hit. If the critical roll is a miss, then the combatant's hit is just a regular hit. A critical hit means that the attacker rolls for damage more than once, as indicated by the weapon description for the weapon that scored the threat, with all the attacker's usual bonuses, and add the rolls together to get total damage.