You could technically play as "evil" even though it was all for the purpose of defeating the Archdemon.
You could kill the elves to ally yourself with the werewolves (or vice versa).
You could keep an anvil of void to get golems.
You could have wiped out the entire circle to get Templar support.
You could have killed Connor or Isolde to stop the demon.
You could even leave Redclife at the mercy of the undeads.
Dragon Age origins probably had the best wrong path without making the character caricatically evil, unlike BG1 and BG2 where playing the evil character was pointless (the game actively punished you for playing the evil character).