Files:
My dank text: https://drive.google.com/file/d/1gg_hkTj7sElCPKklXabHGTRrL6TwRt3s/view?usp=sharing
My dank addon info: https://drive.google.com/file/d/15Dq8ik6A_7wPaIAJRddsBdFnYrML-2fI/view?usp=sharing
An example: https://drive.google.com/file/d/1x0-NSsRhpH7sJA3y2DJodik7h3p2-15T/view?usp=sharing
Source code of the example: https://drive.google.com/file/d/1lT0eh68zjrz_iw2sNdOQCku97s4ovDHr/view?usp=sharing

1. Download my dank txt and my dank addon info
2. Create a folder somewhere
3. Put the addoninfo.txt into that folder
4. Create a folder inside of that folder called "resource"
5. Put the "closecaption_english.txt" into the "resource" folder
6. Open the "closecaption_english.txt" with Notepad, Notepad++, etc.
7. Edit "Witch", "Boomer", etc. to whatever you want to rename that zombie type to
8. Open the bin folder of l4d2 and drag the folder containing the resource folder into vpk.exe
9. Drag the resulting .vpk file into your Left 4 Dead 2 addon folder.
10. Open your game and play. You should see the new names when you kill them!
example of where you can see custom names: "<PlayerName> killed <ZombieType>"

For reference, I have added an example mod for reference[drive.google.com] so you can see how the files are used. I also have the source of the mod[drive.google.com] in case you would like too see inside it and edit it yourself.