I can help spitball concepts! Here's a sampler:
1) Bodyguard. A cop or soldier who returned to private life and got into private security contracting. A consummate professional, meticulous, discrete, and respectful of his clients even when they're pricks.
2) Current or former astronaut! From when you were a kid, you always wanted to go into space. You studied hard, you joined the Air Force, and from there went to NASA. As much or more a scientist as you are a military man, you served a stint on the space station and got to see the planet from orbit. You're driven and know how to dig deep to make what you want happen, but deep inside you're a starry-eyed dreamer too.
3) Deep sea diver. Forget space. We haven't even finished exploring EARTH yet. The mysteries under the sea put barren moons and stormy gas giants to shame. You may have some background in the Navy or Marines, but your main focus is exploration and science. Maybe you're one of the experienced, hardened people who escort scientists on these dives to keep them safe. Maybe you're a scientist yourself. You've stared into the inky blackness of the Abyssals, and seen the alien creatures that dwell within. You've seen sights of incalculable beauty like swarms of glowing jellyfish all moving as one. Things only a handful of other people could claim to have seen. How has that changed you?
4) Actor! Yeah, when you were a kid you got seduced by the lure of high-octane combat sports like MMA. You got into it, and quickly realized that getting hit in the face for 15 minutes SUCKS. It's not that you were bad; hell you were pretty good! It's just that even a good fight was hard and painful and took a toll on the body and mind. Good news was that you were good looking enough, and had enough presence, that you quickly took your career over to acting in action movies. Maybe it was 'fake' fighting...and maybe it's "fake" acting, but hey...the pay's better, the job's better, and people love you even more! Being fake rules!
5) Stockbroker. You're a wolf on wall street; a Patrick Bateman. A power broker, a force of nature. What you see you want. What you want you get. Your body and mind are finely honed instruments, your soul you left behind long ago. It just got in the way. There are not winners and losers in the world; there are losers and YOU. You got into finance not because you have a deep commitment to the idea of trading, but because you assessed career paths and picked the one with the quickest and most ruthlessly meritocratic path to the lifestyle you had chosen for yourself; abject luxury.
And much, much more! (^_^)