The Wrath is supposed to be the second strongest, Darth Marr would be the Wrath if he was indeed the current Wraths better.
Also, Baras>>>>>>>>Thanaton in terms of gameplay
Thanaton blindly threw around his lightning storms, not caring if you were going to be there or not, i killed him with full health almost.
Interresting. I've found Thanaton was always the tougher fight gameplay wise. How it should be LORE wise, is a different story.