After today's episode we were able to learn the roots of Regina's anger. I really felt for her--she had a terribly evil mother who murdered her true love and forced her to marry a man who was revealed in past episodes to not love her and keep her locked away in the castle.
But still, it doesn't excuse anything Regina has done. Here are some of the things I can list, just off the top of my head:
-Ripped out the Huntsman's heart; Killed Graham
-Seperated Hansel and Grettel from their father, after breaking her promise to help them find him.
-Seperating the Mad Hatter from his daughter
-Trapping everyone in Storybrooke
-Killing her father
-Trying to kill Snow
-Framing Mary Margaret for murder
-Tricking the genie into killing the king (though the king kinda deserved it for being a controlling dick, though still... it's evil >>)
There's plenty more that I can't remember. Even after watching that episode and feeling a lot of pain for The Queen, I still think she went excessive in her revenge and hurt too many people who never did anything to her. So I still think Regina is an evil bitch. A relatable one, but still completely psycho and evil.