Worse than the Leicester, Liverpool and City performances? I'm not sure that's possible.
Ole himself came in as caretaker and the bounce that the squad got was instantaneous. And we all now know that pretty much none of that was down to in-depth coaching, it was just down to changing some basics and improving the atmosphere around the place. Those players must currently have little to no faith that their manager and coaching staff have what it takes - you bring in a guy who's been-there-done-that, maybe with a trusted right-hand man, and suddenly those players have a bit of hope and belief again. Players who have been sidelined are suddenly busting a gut cos they see that they have a chance again, and you have a motivated squad again. I mean, you even see it with relegation candidates from time to time - a new guy comes in halfway through the season, and whilst they are still pretty shit they just seem to have a bit more belief, and often end up avoiding the drop.
I see Hiddink retired in September - he's already done the caretaker thing successfully in the PL, if he's fully recovered from Covid I imagine he might be tempted? But that's literally off the top of my head, there must be a few out there that might fit the bill for a few months.