The first is large networks that tolerate spam, and those are irrelevant because their IP blocks are already on every blacklist in the world.
The second is compromised machines, which are the real problem because they're ephemeral. Spammers can compromise a hundred new machines a week. You can't fix them or block them faster than they compromise new ones. The only solution to that is to improve computer security so they don't get compromised to begin with, which has nothing to do with ISPs.
Removing people from the internet is never the answer, both because it's too broad (should the spammers not be able to go to the government's website to pay their taxes?), and because the nominal current source of the spam isn't actually where the spammer connects to the internet anyway.
The better solution if you can actually find a real life spammer is to impose a fine on them that exceeds the profits of spamming.