Jinx
Comet, Arsenal, Plan A, [Plan Z], [5th Augment completely unnecessary, maybe Eager?]
Honestly, with 5 Jinx and 3+ augments, even onslaught mode is trivial. You all just spam R in every direction and it does insane amounts of damage. I beat both 4 augments and 3 augments on first try (4 augments with 0 deaths, and neither attempt needing the second life).
If you're in a random team, go for the same and just carry. With 4 augments, Jinx is really OP (you can build tank items and get insane amounts of AP + AD).
Here's your guide:
https://www.reddit.com/r/leagueoflegends/comments/9fzvfa/easy_543_onslaught_odyssey_augment_guide/
I just linked it in chat at the start of the lobby each time, the randoms were willing to try it and we had no issues. None of us were even playing Jinx regularly.