Is there a quick summary of how much tax various corporations pay?

It's a very tricky problem to solve at the individual company level. There are many things to consider and nothing prevents business from just spending more or moving money abroad to avoid taxes. If a business is big enough to have someone optimising their taxes, they're likely keeping only a proportion of profits in the USA based on how much they want to redistribute to the owners.

In general, Corporate Tax Income is roughly 1-2% of Gross Domestic Product.

Also, big business in the USA lobbies ~3bln per year - it's money going from business to the government, albeit I'd class it more as corruption than taxes.

It's anyway much less than what you pay in %. As it's normal when you have a central corruptible government: whoever holds the more power will get the better treatment. If Amazon leaves the USA, tons of workers are going to become unemployed. If you leave the USA, it doesn't change much (especially because you'll keep on paying taxes until you renounce your citizenship).

I think we’d want real taxes paid, which many people have parroted as ‘zero’ for a long time (I think Sanders claimed this for Amazon recently).

You’d think there would be a simple site where you can look up a company ticker symbol and see a straight taxes-paid number and how much is off-shored to mitigate tax burden.

Smart people use loopholes. They are legal so why wouldn't you pay less tax?

If you hate large companies not paying their share, encourage government to do their fucking job and legislate in order to prevent companies from cheating the fed out of billions. Ironically, (as much as I hate the guy) Trump is the only president in recent history who's made clever moves to target Amazon. Unfortunately, companies lobby to have their tax cheating ignored by congress and government at large.

This is glaringly obvious, when Biden criticizes trump and rich americans for "cheating" on taxes where his returns clearly show he uses similar - sometimes identical means of dodging taxes.

I would like to see which corporations exploit which loopholes: 1) How much they saved on taxes, verses cost of loophole 2) Which loopholes are exploited for the most $.

Publicly listed companies have financial statements by which you can calculate their effective tax rates.

Here’s a quick summary: “very little”.