I'd have character that is retired from an intelligence agency. Not pedestrian agencies like the CIA or NSA, but a serious super secret agency.
Then, have him recruited out of retirement for one last mission involving an old nemesis of his.
Then, I'd have his agency do him dirt any disavow the retired guy.
Then the retired guy could get his nemesis, get the bad guys at his agency, fake his own death, and retire to a South American coffee plantation where he gives the scenery a thousand yard stare.
He also probably has a strained relationship with his daughter.