Rock of Ages
Kill 100 enemies by boulder throw
update thanks to Everharm
This can be unlocked by throwing boulders and other items like crates, vases, etc. Just run towards a group of enemies and when they start following you, run back to the item pick it up and throw it towards the enemy group, if your lucky you can kill multiple enemies with one item. Using this method should net you the achievement fairly quickly.
A trick to this achievment is to turn on the infinite armor power and stone skin power on the enemies, then a single item will kill them, as sometimes the item will only stun the enemy.
Kill an enemy by death fall
see 'Death Rain
Kill 100 enemies by death fall
This achievement should be saved untill the Giant Squid Boss battle, simply get to the stage where the squid turns the crew into Oilmen, then grapple them and throw them overboard.
BEWARE - Do not throw the Oilmen onto the Squid as this sometimes stops the squid transforming the crewmen into Oilmen.
Bring out the Gimp
Kill at least 25 enemies during the Giant Squid boss battle
This will unlock while doing the Death Rain or Fatal Touch achievements.
Slice 'n Dice
see 'Meat Market
see 'Meat Market
This achievement can be fairly easy, I found the 'Blade Fury' Dual Wield Parry attack to be quite useful as it removes an enemies Head, Arms and Legs! Thats 6 dismemberments per enemy! Other useful moves include 'The Mercenary' Dual Wield X,X,X,Y, and 'Triple Heavy Strike' Dual Wield Y,Y,Y.
Perform every parry kill move
There are 3 for each weapon style: One-Handed, Dual Wield and Two Handed. Simply wait near an enemy and just as his attack is about to hit you, press LT to block, then press the button displayed above his head either X,Y, or B, perform all three then change to the next weapon style.
100 parry kills
see 'Parry King
200 parry kills
Just kill every weak enemy that you see with a parry attack and you should have this achievement in no time. This should also help towards the Meat Market achievement if you try to perform the X parry while dual wielding.