In the Iliad, what happens because of Achilles' anger? What are three consequences?

The first consequence of Achilles' anger is that withdraws from the fighting and remains lounging in his tent. Shakespeare has comic scenes involving Achilles amusing himself in his tent along with Patroclus and the scurrilous clown Thersites in the play Troilus and Cressida. 

The second consequence is that without Achilles the Trojans are the superior fighting force. This is largely due to the leadership and example of their great hero Hector. Without Achilles, the Trojans begin overpowering the Greeks and driving them back towards their ships. Many Greeks appeal to Achilles to rejoin the fighting, but he is adamant. He wants them to appreciate how much they need him.

The third consequence is that Achilles' friend Patroclus borrows Achilles' armor in the hope of frightening the Trojans, who have advanced so far that they are fighting among the Greek ships and trying to set fire to them. But Hector slays Patroclus, thinking he is slaying Achilles. The death of his friend so enrages Achilles that he gives up his sulking in his tent and goes out to fight. He chases the entire Trojan army back behind the walls of Troy, with the exception of Hector, who decides to fight Achilles single-handedly. This is the climax of Homer's Iliad. Achilles kills Hector and drags his body around the city behind his chariot. Without Hector it seems obvious that the Trojans are now destined to lose the long war. There is a great feeling of gloom and foreboding among the Trojans at the end of the Iliad.