Vader murdered children. The aforementioned kid Jedis. Plus between him and the Emperor, they make make Hitler's extermination of the Jews look like a drop in the bucket. But, yes, all he had to do to be redeemed was toss the Emperor.
Also didn't like that they edited ROTJ and switched out Sebastian Shaw for Hayden Christiansen as Anakin's Force ghost. Why, exactly, does Anakin's ghost get to be young, but Ben and Yoda's stay old? Is it a statement that Anakin `died' when he became Vader?