The Choedan Kal are two giant sa'angreal that were created during the War of Power, one for a man and one for a woman. They are the two most powerful sa'angreal ever created.
Rand was successful in cleansing the taint from saidin, but in the attempt, the female access key was destroyed as well as the sa'angreal itself. The male counterpart remained in Rand's possession.
However, later he draws in as much power as he can through the sa'angreal and drives it back through itself, purposely obliterating it.
The Sa'angreal especially the CK which were the most powerful ever made would have made last battle much easier. Rand could've used it to destroy the numerous shadow spawn with it. It was more powerful than Callandor without the flaw.
Why is it that then Rand intentionally destroyed it?