In recent times there have been a sudden influx of LUA scripters that constantly change their name so it is difficult to get their STEAM ID. I have provided a full proof way of making sure you ban the right one.
1. Shift+Tab
2. View Players
3. Pick the correct profile pic
4. Get his steam community url
5. www.steamidfinder.com
6. Put the steam community url into the designated area
7. Hit the button
8. Go to the Source Bans page and input the proper information
9. Hit the Upload Ban Button
10. ????
11. PROFIT!!!