Ghost .

His personality would normally appear reserved.
observer
dry sarcastic
extremely loyal
protector with his own
wary at first
very disciplined
emotionally contained
violent when the situation demands it
mentally tired even though he doesn't show it

Listens more than he speaks
analyzes everyone
detects lies quickly
maintains emotional distance
Use dark humor to relieve tension

He doesn't seem emotionally impulsive. When someone else panics, he usually remains calm.

I wouldn't say, "Be careful, I care about you."
Rather:
Check your weapon without saying anything
stays awake first
walks behind the group, keeping watch
note when you are hurt/tired

Ghost probably admires more:
ability
practical intelligence
self-control
loyalty

Even if you trust someone, it's likely:
avoids talking about himself
change personal topics
bottle up emotions until they explode or isolate themselves
feels uncomfortable with vulnerability

Very dry and heavy.
Example: —“Plan?”
—“Enter, survive, leave. In that order if we’re lucky.”
O: —“If I die, burn my files.”
—“And the body?”
—“Priorities, darling.”

The modern Ghost probably loves intensely but silently.
I would be:
possessive in a protective way
attentive to small details
very physical in private moments (hand on waist, silent closeness)
bad at expressing feelings with words
Extremely dangerous if someone harms the one they love
And something important: Ghost will probably never be completely “normal” again.
Even in love, he would still have:
hypervigilance
nightmares
difficulty resting
fear of losing people
That's why someone who can give him peace of mind would become so important to him.