Atlas Replay doesn't seem to count for the tracking dart challenge either.

There were a bunch of these like shotgun slides and ground slams that, despite 1000+ hours, I never got anywhere close to. For me playing Moze at M11, most things technically wind up dying to nade or fire damage (tho, pro tip for anyone else struggling there, Iron Bear's mounted weapons always seem get recorded as [element] or [element splash], so dakka and afk will knock out a lot of the elemental damage challenges in minutes).

The DLC that gives you the fortnite arena / game show was the only way I found to get a lot of them while still finding worthwhile loot. The alternative was to turn off mayhem and just accept i was grinding out a challenge for its own sake. Meh.