Here is the full list of all 87 I, Gladiator achievements.
Play IG every day for a month
Defeat Spiculus unarmed
Complete 240 laurel challenges
Reach 50th level
Run 100 kilometres
Play IG every day for a week
Shed 1000 litres of blood in the arena
Dodge lion's attack 50 times
Destroy 50 totems
Send 50 opponents into 'Bond of Rivals' trap
Go through the block 30 times
Win in the arena, hitting nobody
Dismember 50 opponents with the 'Iron Vortex'
Dismember 25 opponents with the 'Iron Vortex'
Stun 30 different opponents with a mace
Kill an enemy with the weapon thrown by spectators
Dismember three persons with one blow
Reach 25th level
Hit 50 opponents when they are foot trapped
Buy all helmets and armor
Hit 25 opponents when they are foot trapped
Defeat Spiculus armed
Burn 50000 kilocalories
Dismember 200 opponents entrapped in 'Bond Of Rivals'
Use 20 different types of weapon
During one fight kill three opponents with three different traps
Complete 100 laurel challenges
Defeat Biork the Berserker
Destroy 20 totems
Perform a 16 hit combo
Burn 5000 kilocalories
Send 25 opponents into 'Bond Of Rivals' trap
Defeat Kolhid the Monster
Kill 10 lions
Run 25 kilometres
Drive 1000 spectators to the tears of happiness
Dismember 50 opponents entrapped in 'Bond Of Rivals'
Being knocked down 100 times
Win for the first time in the Insequitur with totems
Shed 100 litres of blood in the arena
Count 500 stars
Dismember 5 enemies in a row
Reach 10th level
Hit 5 opponents when they are foot trapped
Kill 500 opponents
Dismember 5 opponents entrapped in 'Bond Of Rivals'
Kill four enemies within less than 30 seconds
Defeat Cathbad the Druid
Dismember 5 opponents with the 'Iron Vortex'
Destroy 5 totems
Kill a lion
Kill 3 lions
Win for the first time in the Exterminator
Send 5 opponents into 'Bond Of Rivals' trap
Fry 50 opponents in 'The Dire Of Daith'
Fry 25 opponents in 'The Fire Of Faith'
Drive 300 spectators to the tears of happiness
Impale 50 opponents on spikes
Impale 25 opponents on spikes
Count 250 stars
Being knocked down 50 times
Enter the fight with no weapon and win
Impale 5 opponents on spikes
Count 100 stars
Perform a 13 hit combo
Lose 15 times in a row
Being knocked down 20 times
Lose 10 times in a row
Lose 5 times in a row
Reach 5th level
Fry 5 opponents in 'The Fire Of Faith'
Run 5 kilometres
Drive 100 spectators to the tears of happiness
Kill an enemy with the weapon of the other defeated enemy
Dismember two persons with one blow
Complete 10 laurel challenges
Kill 100 opponents
Perform a 10 hit combo
Shed 10 litres of blood in the arena
Burn 500 kilocalories
Kill 20 opponents
Shed blood of 30 different opponents with a sword
Kill an enemy without receiving any damage
Kill three enemies within less than 40 seconds
Win for the first time in the Pugnator
Win for the first time in the Insequitur with other gladiators
Complete all 3 laurel challenges in one fight