"Two Birds, One Stone" achievement...

[Kutar'k]

Where can i do this?

[Dark Bison]

Anywhere really, if there are a lot of enemies you can trap them in a hole you dug under a rock and then drop it on them.

[蜗牛大魔王]

Cactus, they don't move.Rock will crash some weak area such as sand.

so if you find it's hard to aim moving enemies,maybe you can try "Two Cactus,One Stone"

[InstantPhoga]

I got it without even knowing it.

[B〄F Altonator]

I literally killed 2 "birds" with a giant stone while they were flying and not trapped :P