A Robin Red breast in a Cage Puts all Heaven in a Rage. (5-6)
This is the first of Blake's animal couplets—and it sets the pattern for the rest. A small example of a bird suffering and losing its freedom really reflects all suffering and the death of all freedom. It's enough to tick heaven off.
A dog starv'd at his Master's Gate Predicts the ruin of the State. (9-10)
Like the robin one, this couplet shows how a smaller example of cruelty can reflect greater sufferings. If the relationship between a dog and its master gets this bad, it probably means that the master isn't treating the humans who work for him very well either. The whole social order might fall into revolution—or pure tyranny.
He who the Ox to wrath has mov'd Shall never be by Woman lov'd. (31-32)
This one might seem silly—but Blake's saying that, if you're in the habit of picking on innocent animals, you're probably not going to appear very lovable to humans either.
The wanton Boy that kills the Fly Shall feel the Spider's Enmity (33-34)
This one's interesting. Blake is implying that there's some kind of karmic law at work in the universe—if you kill flies, you're going to find out what it's like to die as a fly. Even though there's suffering in the world, there's also justice.
The Babe that weeps the Rod beneath Writes Revenge in realms of death. (73-74)
This couplet is about human suffering, specifically—unlike the other couplets, which mostly deal with animal suffering. Like the one about the boy killing flies, this couplet also implies that there's some kind of cosmic justice at work in the universe: the abused baby will be avenged.
The Harlot's cry from Street to Street Shall weave Old England's winding Sheet. The Winner's Shout, the Loser's Curse, Dance before dead England's Hearse. (115-118)
This one is more about social injustice than specific individual examples. The plight of poor women who've been forced into prostitution and of losing gamblers will eventually help run England into the ground, and destroy the nation.