Dead Rising
50 Achievements
1,000
40-50h
Self Defense
Defeat at least 1 psychopath.
20
12.39%
How to unlock the Self Defense achievement in Dead Rising - Definitive Guide
You will easily kill 10 psychopaths if go out of your way to every mission (or do Saint achievement), you just need to remember to keep full film on you and take a picture of the psychopath right before killing them off. I also recommend obtaining the Megaman blaster first so you can 1-2 shot the psychopaths.
I did this on my 2nd playthrough missing Kent and the Butcher make sure to take a picture of the psychopath(s) before going anywhere (I believe you can take a picture of the dead bodies) to get the photo pictures.
Kill 1 psychopath. Note that Carlito, Isabella and the convicts in the Jeep do not count towards this achievement. There are 12 total in the game:
Name: Cletus the angry gun shop owner
Location: Huntin' Shack
Call Time: Towards the beginning of the game
Name: Adam the clown
Location: wonderland Plaza
Call Time: 9:00 p.m. September 19th
Name: Cliff the Vietnam Vet
Location: North Plaza
Call Time: 8:00 a.m. September 20th
Name: Kent
Call time: after you beat his side missions
Name: Jo the cop
Location: Wonderland Plaza
Call Time: 1:00 p.m. September 20th
Name: The Halls (3 snipers)
Location: Entrance plaza
Call Time: 4:00 p.m. September 20th
Name: Sean the cult leader
Location: Movie land
Call Time: 12:00 p.m. September 21st
Name: Paul Carson, the Arson
Location: Wonderland plaza
Call Time: 6:00 a.m. September 21st
Name: Steven Grocery store Owner
Location: Grocery Store, North Plaza
Call Time: Case 2-3
Name: Larry the Butcher
Location: Butcher shop in maintenance tunnels
Call Time: Case 8-4
Here's a link to well written guide on the psychopaths:
click here