Is it possible in counter strike source to increase weapon-damage (in a bot-match) so that everyone gets one-shot kills?
You can't do this client sided, or at least, legally. A client side modification would be a hack and in the event of attempting to do this you will likely get VAC'd.
You need a server side plugin to do this for you. Whether you create a local game on your computer or connect to one online, you are still playing in a server environment. When you start a game on your computer it creates a server with your local IP and connects you to it.
The easiest way for you do do this for yourself playing with bots would be to install Sourcemod in your cstrike folder. It's in
There you will create a
After download this plugin and place it in the plugins folder. [CSS] Weapon Mod
Set up the cvars/configuration files to your needs. It looks like you're looking for:
Then once you create a local server the plugin will load and you'll have your damage.
You should look at a headshot only script. I think there will be something in it about this since headshots do way more damage than they are supposed to do.