STEP 1:Go directly to your steam library while you're in garry's mod
STEP 2:Right click on Garry's mod
STEP 3:click the ''uninstall" button
STEP 4:Cry for 2 hours because you have just realised that you have to re-install the whole game and you've got a sh*tty internet connection, cuz you just NEEDED to live directly in ♥♥♥♥♥♥♥♥ nowhere, Orlando, meaning you'll be a dead man before the game has even started downloading again.
STEP 5: (only use when you've already waited for 2 hours) Press Steam on the top left of the screen, press settings, then go to Downloads. After you've done that, you just throw the whole PC out of the window. (preferably while that one neighbour you hate is walking in front of your house at that excact moment)
STEP 6: profit.

Congrats! you have just defeated the final boss in garry's mod!
Let's be real though, it wasn't THAT difficult, was it now?
Hopefully this guide helped you with defeating the boss.
Love - The boss-deafeating team.