If you are a new player of GW2 and want to grind on achievements, you may notice that there are around 7 achievements that are impossible to get as of 2022. However tho, I have figured out a way to get the achievements which is how I was able to obtain it, and can be useful to any players that have yet to obtain it as well.

Unfortunately, this method only works on PC so if you also play on console than I cannot help you with that.
To start off, you need a mod tool (I would recommend Frosty Mod Manager[frostytoolsuite.com], the most common modding tool for GW2) and the Private Play Remastered mod that grants you access to tons of game modes and maps you wouldn't otherwise access in vanilla private play. Pretty cool right?

Mods:
Private Play Remastered[drive.google.com]
Cats vs Dinos AI Generator[drive.google.com], the default Cats vs Dinos mode has no AI but this addon generates AI for the mode.

Btw, these mods are not by me all credit goes to BreakfestBrainz2., and ElectroRoBro (electrorobro on discord)
You can otherwise access these mods in the GW2 Frosty Modding discord server.

This is a mod by Mr Jt that can also unlock the achievements for you.
How this mod works, is that upon getting killing a weed or a browncoat; it will trigger an event that unlocks the Community Challenge achievement that would otherwise be triggered upon legitimately reaching the steps for the achievements.

Mod Link[drive.google.com]

As of 2024, the EA anticheat has made applying mods incredibly difficult. It is not impossible however.
Here I will explain a step-by-step instruction in order to apply mods for this game, if you would rather watch a video instead then here is the video I will be referring to:

• Install Frosty Mod Manager from the link above this guide, then install FrostyFix[github.com], the mods linked from this guide and a modified https://drive.google.com/file/d/13n2mgWVjUG_t_5nfAVIZCTKR-vyUBmbc/view?usp=sharing file
  
  
• Delete the original FrostyModSupport.dll file and replace it with the modified one linked above
  
  
• Open the FrostyModManager and add the main GW2 file. As you usually should, add & apply your mods (Private Play Remastered in this case).
  Now, if you are using FrostyModManager for the first time; then launch the game. This will not apply the mods but will add the necessary installations for Frosty to work for GW2. After opening GW2, close the game upon the cutscene playing.
  
  
• Exit EA Desktop. Open Frosty Fix, select the platform you are launching GW2 on and click Launch with Mods Enabled. Wait until the cutscene happens, then exit out the game. Otherwise the backyard will boot up with unapplied mods.
  
  
• Now here comes the magic, Launch Mod Manager and Launch the game through the software once again! And Tadaaaa! It works like a charm!!!
  

I've been getting a lot of comments saying "just use SAM instead!!!" (Steam Achievement Manager), and while yes that is an alternative solution; the whole point of this guide is to reveal legitimate methods in getting the impossible achievements for this game.
Most people, including me, find it more fun to work hard for the achievements.

In conclusion, if you want to get the locked steam achievements via legitimate methods then follow this guide as it works perfectly.
Thanks for taking the time to read this and have fun :)