Download AutoKeyClicker v1.2.3 zip, it's a free software, you can google the name.
Open the autokeyclicker and set it up like this don't start it yet.
Then open the game, go to professional levels and choose Music LvL. Now start the autoclicker go back fast to the game and leave the cursor on the Undo menu when the level fails. The autoclicker will execute these keys: "O", "P" and "Mouse1" same time every 200ms.
You should do around 125 kills every 13 seconds. This way your keyboard will thank you ;)
I did the first 14 achievements without this software pretty easy in the same level but got bored and tried something else for the last one.
https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=2054864137