To complete this achievement you need to kill the criminal from broken valley and orobas fjords, 5 in each map totaling 10 criminals. The criminals in broken valley have to be killed before you adquire the battle tower as broken valley will be filled with deadly smoke and you wont be able to do this.
Be extremely carefull and DO NOT SELL OR DESTROY ITEMS DROPED BY THEESE OUTLAWS YOU WILL NOT BE ABLE TO FINISH THE QUESTS IF YOU DON'T HAVE THEM!
In Broken Valley you get your quests in the barracks (the building you have where commander Rhode is waiting for you to bring informations about the dragon sightings), in there you will find a sign with some papers on it, you have to read it to accept the quests. In Orobas Fjords you get your quests in the Champion Harbour, by entering the door on the right side you will find the same sign on top of the balcony. To finish the quests you have to talk to the respective captains, located in the vicinity of the bounty boards, and bring the item you are requested.
Broken Valley criminals:
Hjalmar - located in the goblin camp near the chapel, he is a beholder, one of the easier to kill
Hallorn - He is in the secret tunnels under Broken Valley. It has three entrances, one next to the teleport in a goblin camp on the mid-east side of the map, and another close to lord lovis tower.
Yup'ik - He is in a small goblin camp right to the black ring controlled mine blown up in a cut scene (it looks like a fortess from outside).
Jagon - He is in the Temple of the Dead which is located in the bandit camp, he is the thoughest of them all, and the temple has a puzzle. To avoid poison in the first room follow the dead bodies and blood, beware the skeletons. when you get outside follow in through the river as the fiery floor will burn you to death if you dont touch the water in time.
Viper - Just next to the southernmost teleport, close to one of the gremory brothers, beware his camp is well guarded and you will die fast if you're not up to level and not careful enough.
Orobas Fjords criminals:
Barnabus - He is in a cave not far from the knight statue, if you select Igor as your necromancer he is also the sorcerer you have to kill to finish his upgrading quest
Alrik - Southeast from the harbor on a cliff is an imp camp, its located left to Keara's Flying Fortress, and close to Moor.
Moor - Once you got Alrik, just fly to the other side of the river and a bit south, Moor will be waiting on a cliff with a teleport, this cliff is close to the anti dragon zones do it's hard to miss.
Alutiiq - He can be found in the Depleted Ore mine, the location is surrounded by imps, just follow the westmost coast in the map it is located left to the island where Stone's Flying Fortress is. (the imps outside can surprise you if you're low leveled and drop by the entrace bye exiting your dragon form, procced with caution.
Ragon - He is located in Dark Cave, wich is close to the fortress where you deactivate those anti-dragon barriers, it is also the same cave where you find the book for Barbatos.