This is the fastest and probably only realistic way to earn the five ranked achievements (10, 20, 30, 40, 50). Online is dead, and from what I can tell the servers are getting a bit shoddy.
You’ll need a boosting partner and an extra controller. Our goal is 210 stars to reach rank 50. Since losing matches equals losing stars, we’ll be using a guest account to take all the L’s.
Sign in as guest with your second controller and start the game. You’ll be required to complete the short tutorial. Search for online 2P matchup with your guest to be matched up with your boosting partner. They can win and repeat piling up stars/ranks while your guest account absorbs the losses.
Switch as necessary. We switched every 10 ranks. You will have to do the tutorial every time your guest account starts back up.
Servers started acting up when we got to rank 35 or so. Guess account worked fine but main account would have to quit to console and restart after every win.
A grind regardless, but nice ratio!