The existing common equity (and IIRC preferred stock) in a number of entities was massively diluted by issuing new preferred stock and warrants to the US government.

Here are two examples, they were among the worst offenders. Look at the share price for Citigroup and AIG:

https://finance.yahoo.com/quote/C?p=C https://finance.yahoo.com/quote/aig/?p=aig

If you owned pre-crisis C common stock, you're still down about 84%. If you owned pre-crisis AIG common, you're still down about 95%. (that's approximate, done by eyeballing the charts). Edit: Yahoo Finance charts have been getting worse and worse, you need to click "Max" to see the proper timeline.

I don't follow UK equities closely, but I think the same thing happened to a number of UK banks at the time. E.g. RBS.

Unfortunately the whole thing was quite uneven. E.g. Goldman Sachs took advantage of the morons at AIG who sold them very cheap "insurance" such as credit default swaps. But Goldman was made whole. What should have happened is that Goldman should have been made to share the pain.

Edit: I'm of course talking about the '08 financial crisis in general. I don't agree that the Libor scandal was significant enough to nationalize the banks as punishment. I'd much rather see a few bad actors taken out back and shot. That would be much more salutary in terms of deferring future bad behavior.