Here is the full list of all 15 Dismantle: Construct Carnage achievements.
Win your very first match
Win ten matches
Beat a team of 3 Gladiators (or above)
Place last in a Free For All match against of 3 AI of Gladiator (or above) difficulty
Beat a team of 3 Legendary Champions
Break at least 100 Weapons
Chew off another player's leg
Win 50 matches
Slap an opponent with their own dismembered arm
Remove a limb using another player's head
Remove a limb using another player's torso
Win a match with 3 or more competitors without losing a single limb
Participate in a Tiebreaker
Win with triple the points of your closest competitor
Win a round without dismantling any opponents