Can someone who becomes a Red Lantern become "good" again i.e. control the anger and return to normal?
The best example of this is Razer, a Red Lantern who rejects his anger, trains with the Blue Lantern Corps, and is eventually followed into space by a blue ring (indicating he'll be the next Blue Lantern).
There are also other examples that, admittedly, adhere less to the spirit of your question.
Green Lantern Guy Gardner once gave into his rage and wielded a red ring for a time:
Green (and then White) Lantern Kyle Rayner once wielded all the rings simultaneously.