You can filter here to show the SpaceX group, which is a whole bunch of Falcon 2nd stages. It isn't like anyone else puts effort in to deorbiting their 2nd stages, SpaceX just launches the most.

https://sky.rogue.space/

They also dump Dragon 2 trunks and used to dump some Starlink deployment hardware (which I think is now attached to the 2nd stages), but those two examples are in such low orbit that they don't last long.