Plants vs. Zombies: Battle for Neighborville

The way I got this was by playing on a private game at Giddy Park (the amusement park). With it being on private, the only things that were spawning were the television zombies, which are easier zombies to kill.

Unless you are good at avoiding shots with the onion while still dealing damage, I personally recommend just using the potato bombs and automatic fire (precision shots are much slower).

I found a location where you can plant potato bombs and the zombies will walk over it almost every time. I have attached a photo showing where to approximately place the potato mines to the left of the ride that has the platform that goes up and down (near the zombie spawn point). Just in case the image doesn't load for you, put one right on the track where the stairs line up with the track that guides the two platforms that go around the map, and one at the bottom of the top flight of stairs. They were walking over them every time.

https://imgur.com/a/pHKxkFd

The easiest way I've found to grind all the 200 vanishes achievements was to keep playing Bingo Bongos battle chest challenges in Town Square. Specifically Rangled Renegades, you can just stick to one zone the entire challenge and have several enemies come your way!