In an effort to counter all the negativity of Anders in the last few posts I'm just going say:
Anders is a hero. 
Anders is so far from a hero that he couldn't see the neon green word Hero from the orbit where I wish I could throw him.
Mages are not oppressed in all corners of the world and he's not even originally from Kirkwall, ya know that major city that he blows up one of the largest buildings in and kills hundreds if not thousands of possibly innocent people. He no longer had a phylactery for the Templars to follow him so he could have just disappeared without a trace into an area where mages were less oppressed (such as Orlais) or gone into Tevinter where mages are pretty much king. He could have helped mages by getting them an escape route to one of the other areas of the world instead of making it even worse on them by just making people hate and fear mages even more.
Also he has seen first hand not only Hawke, but the Warden or the Warden-Commander of Orlais (if you played DA:A without your Warden) turn the world around in a very short period of time. Instead of following their example he decided it was best to destroy a large number of people for the sake of his personal crusade and it didn't even mean anything. Instead of believing in his friends, such as Hawke, instead of using them like pawns in a sick game he could have changed the world without 'collateral' damage.
Very few people believed what really happened in Kirkwall even when they were told by someone like Cullen, which is proved by Cassandra's utter disbelief at Varric's story. It wasn't until later that the Circles shattered and Kirkwall was a footnote in the reasons why.
My biggest problem with the character of Anders is the sheer lack of his awareness of the world around him. He's met not one but two of the 'greatest' heroes of the Dragon Age universe and they can do things with or without violent means. He's a character assassination of himself as by the end of DA:A and part way through DA 2 it seems that he's starting to realize that things can be done without a total loss of life, and then chooses to put his friend (and possible romantic partner) in the dark and kill off innocents anyway.
Depending on your rivalry or friendship he may or may not admit that he perverts the noble spirit of Justice into Vengeance. He'll either claim that he shouldn't have taken Justice within himself or he'll claim he was in full control. He then puts himself at the mercy of Hawke in either option which is another sheer assassination of the freedom demanding Anders who would probably have gone down fighting especially considering he was still fueled by the Spirit of Vengeance (Penance Stare not included).
He's well written up until he whines one too many times about oppression, when he moved into Kirkwall which is pretty much the most oppressed area for Mages ever and knew that in the first place (since he wants to make an example at the 'heart of darkness'); and when he chooses to kill people that were trying to help him such as the Divine and chooses to use his friend Hawke as a diversion to guarantee his terrorist action is successful.
He's one of the worst example of flip-flop writing in the entire series.