Please note: all credit goes to CaptainMorghan!
This is a guide to get all player kill achievements in a single player world without the use of mods.
How to Obtain Alexander The Great Achievement
Now there are currently two ways to get this achievement (and other player kills related achievements) and that is doing it legit (which requires a boosting partner and several hours) or by doing it by yourself in a single player world. To do this all you need to do is load an older version of the game which had an npc that counts as a player kill.
Right click 7DTD in your library and go to properties then click Betas, this will open a drop down list of all the previous versions, the one you want to select is alpha 15.2 Stable. Once selected this should start downloading the new version through steam (you can check its progress by clicking downloads at the bottom of your screen) Once it’s done downloading you can move onto the next step.
Launch the game! once its started create a new game and in the game options turn zombie spawning off (this isn’t necessary it just makes it so you don’t have to worry about other zombies. Once that’s done start your new world
Once in your new world press F1 to open the console, once open type dm and hit enter then type cm and hit enter. This will enable the Creative Menu and the Debug Menu.
Open the creative menu by pressing u and select some blocks/weapon I would recommend the rocket launcher for the splash damage because you will be spawning several bandits(the npc’s that count as player kills). Now with your blocks build a a medium sized pen so that way the bandits cant run away. and then build a small tower so you don’t kill yourself with splash damage.
Now to actually spawn the bandits press F6 on your keyboard to open the Entity menu which will allow you to spawn any entity in the game. Now the Entity you want to spawn is a melee bandit spawn as many as you would like in your pen that you built in step 4 I recommend only spawning 10-20 if you have a low to average pc because it will cause lag. Note: where your cross hair is pointing is roughly where the bandits will spawn so make sure you are looking inside the pen.
Now this is important before you kill the bandits you must exit debug mode and creative menu to do this simply press f1 again and type dm and cm into the console to exit them. Once Creative menu and debug mode are now off you may now kill the bandits and every kill will count towards the achievements.
You need to kill 250 of these bandits to get the achievement so you will need to switch in and out of the debug menu in order to spawn more, it shouldn’t take to long (it took me about 10-15 minutes) to get all 250 achievements.
Congratulations now you can get the achievement and can now easily get 100% completion of 7DTD without even having the hassle of going to multiplayer servers or finding a boosting partner.