Fighter enhancements (history)

Level 1

 * Skill Tactics I: Grants a +3 bonus to Intimidate and Tumble skills
 * Skill Recovery I: Grants a +3 bonus to Heal and Repair skills
 * Item Defense I: Grants a 25% chance to negate item wear when it occurs
 * Fighter's Action Boost I: Grants the ability to receive short term boosts to attacks (+3 to hit), Armor Class (+2), or attack speed (5 uses, lasts 20 seconds, cooldown 30 seconds)
 * Fighter's Combat Expertise I: Grants an additional +2 bonus to armor class while using the feat Combat Expertise, but reduces the attack as well by 2 more points (Prerequisite: Combat Expertise)

Level 2

 * Fighter's Strength I: +1 Strength
 * Armored Agility I: Reduces armor check penalty by 1
 * Fighter's Mobility I: Grants an additional bonus to armor class while tumbling (Prerequisite: Mobility)

Level 3

 * Skill Tactics II: Grants a +4 bonus to Intimidate and Tumble skills
 * Skill Recovery II: Grants a +4 bonus to Heal and Repair skills
 * Fighter's Action Boost II: Grants the ability to receive short term boosts to attacks (+4 to hit), Armor Class (+3), or attack speed (5 uses, lasts 20 seconds, cooldown 30 seconds)

Level 4

 * Item Defense II: Grants a 33% chance to negate item wear when it occurs
 * Fighter's Dodge: Grants +1 to Armor Class (Prerequisite: Dodge)

Level 5

 * Skill Tactics III: Grants a +5 bonus to Intimidate and Tumble skills
 * Skill Recovery III: Grants a +5 bonus to Heal and Repair skills
 * Fighter's Strength II: +2 Strength
 * Fighter's Mobility II: Grants an additional bonus to armor class while tumbling (Prerequisite: Mobility)

Level 6

 * Fighter's Combat Expertise II: Grants an additional +4 bonus to armor class while using the feat Combat Expertise, but reduces the attack as well by 4 more points, for a total of +9 AC, -9 Attack. (Prerequisite: Combat Expertise)
 * Armored Agility II: Reduces armor check penalty by 2
 * Fighter's Action Boost III: Grants the ability to receive short term boosts to attacks (+7 to hit), Armor Class (+5), or attack speed (5 uses, lasts 20 seconds, cooldown 30 seconds)

Level 7

 * Skill Tactics IV: Grants a +6 bonus to Intimidate and Tumble skills
 * Skill Recovery IV: Grants a +6 bonus to Heal and Repair skills
 * Item Defense III: Grants a 50% chance to negate item wear when it occurs

Level 8

 * Fighter's Strength III: +3 Strength
 * Fighter's Mobility III: Grants an additional bonus to armor class while tumbling (Prerequisite: Mobility)

Level 9

 * Skill Tactics V: Grants a +7 bonus to Intimidate and Tumble skills
 * Skill Recovery V: Grants a +7 bonus to Heal and Repair skills

Level 10

 * Armored Agility III: Reduces armor check penalty by 3
 * Fighter's Action Boost IV: Grants the ability to receive short term boosts to attacks (+x to hit), Armor Class (+x), or attack speed (5 uses, lasts 20 seconds, cooldown 30 seconds)
 * Item Defense IV: Grants a 67% chance to negate item wear when it occurs

Unconfirmed
The following enhancements appear in the game data files but their implementation has not been confirmed yet:
 * Extra Cleave I and II