Okay so I have a problem with how boomerangs work, and I have a player who really wants to use a boomerang as their main weapon. My problem is that boomerangs do a 1d4 damage, which feels like too little in my opinion, considering historically they have been strong enough to bring down kangaroos and emus, no simple task. The obvious work around to this is to homebrew boomerangs as a martial weapon dealing 1d6 damage, but another way could be making an improved version of a boomerang that does more damage, like 3.5e's giant boomerang. I think the best idea for this would be a bladed boomerang, but a bigger boomerang could work too. I'm curious if other people think that boomerangs need work or if they're just fine.

The “stronger” version of a boomerang is a javelin.

You could potentially give them an increased chance of a critical hit against beasts, if you're after some flavour.

Ultimately, boomerangs are just spinning sticks - the killing of kangaroos and emus came (IIRC) from hitting them on the neck (not so small a target on an Emu!). But then, if you're going realism, any hit with a sword is death, so you need to take it with a heap of abstract salt!

Bladed boomerangs, magical sonic boomerangs, lightning boomeranges etc., or having the added mechanic that if it misses, in the next round of combat it will attack the same target again unless they move (as the boomerang comes back) could add some flavour, though that last one needs a lot of caveats (hitting other things, that sort of thing).

I suppose, as a boomerang flies more than arcs, you could make it a line attack - attacking each creature on the line until it hits. Dex save or be hit, basically, and only the closest who fails gets hit. That could make it more interesting, without outright making it do more damage!