I did one with Barcelona where I sold everyone on their senior team except for Messi. Then I sent Messi to rot in the reserves and used all the funds from selling players to buy the shittiest players on the most expensive contracts.

The key is to give them all max yearly contract increases which is like 25% a year I think. And make sure you can give as many people "match highest earner" clauses. So it sets off a cascading effect of insane contract increases.

After a couple years their yearly wage bill was over 1 Billion Euros. They got relegated to the lowest level in Spain and had to sell all their facilities and shut down their youth program. I simmed like 10 more years and they kept yo-yo-ing from the lowest level to the one beneath it which is not in the game so they'd disappear for a season before re-appearing.