Lews Therin's situation was an impossible one. It called for an extraordinary man, and he was indeed such a person.

If your definition of perfect is that he is infallible in every context, in the face of every possible challenge, and basicaly "godlike" then nobody will meet those requirements.

But if you look at Lews Therin, he was a super-achiever, and yet he remained committed to serving his fellow humans. I haven't seen a single charcter flaw in him.

The fact that he was defeated and went mad is a testament to the severity of the challenge he faced. All indications are that if not for him, the Light would not have lasted the 10 years that it did.

It is best to therefore judge him by saying that he was inadequate for the task at hand, but more adequate than anyone else on earth.

In other words, no one could have done better than him. And despite his superiority to his fellow humans, he remained a surprisingly gentle, loving, merciful, kindhearted, generous and inspiring human being.

Now, most readers don't like "perfect" characters, but that's just tough, because Lews Therin was pretty much as perfect as you can get while still remaining human.