Has a Leaguer ever fully crossed over to the Legion of Doom?

I know Jordan became Parallax for awhile and Jason Todd was a baddie before he was developed into an antihero, but has a member of the JLA gone "full bad" without being written back into redemption? I think that would be an interesting development. One that betrays them and just becomes a teammate on the bad side.

-- Sent from my 13 year old P.O.S. Desktop®