MORDHAU

This achievement is (AFAIK) only obtainable on the Mountain Peak map, as it's the only one containing icicles. A good thing about it, though, is that every mode playable on this map has an area with icicles accessible to everyone (they are limited, so make it count).

You cannot pick up an icicle, which means you need to shoot/throw something at the icicle for it to drop down. Your enemy has to be right under it at the same time to be killed by the icicle. If you happen to see an icicle kill in the killfeed, you should unlock the achievement shortly after.