It's ironic that, on their first date, Wade tells Vanessa that he wants to get to know her, "not the short-shorted, two-dimensional sex object peddled by Hollywood." By the end of the film, that's exactly what she becomes: a cardboard damsel in distress.
It's Like Wade Made Her in a Computer
She doesn't start out so banal, though. When we first meet Vanessa, she's obviously not the typical superhero girlfriend.
For starters, she's a prostitute. It's hard to imagine Captain America or Ant-Man dating a call girl; just sayin.' Secondly, she's just as warped as Wade. Check out what passes for banter and bonding between them the night they meet:
WADE: So you, uh, bump fuzzies for money?
WADE: Rough childhood?
VANESSA: Rougher than yours. Daddy left before I was born.
WADE: Daddy left before I was conceived.
VANESSA: Ever had a cigarette put out on your skin?
WADE: Where else do you put one out?
VANESSA: I was molested.
WADE: Me too. Uncle.
VANESSA: Uncles. They took turns.
WADE: I watched my own birthday party through the keyhole of a locked closet, which also happens to be my—
VANESSA: Your bedroom. Lucky. I slept in a dishwasher box.
WADE: (Gasps) You had a dishwasher. I didn't even know sleep. It was pretty much 24/7 ball gags, brownie mix, and clown porn.
VANESSA: Who would do such a thing?
WADE: Hopefully you, later tonight?
They hit it off, at least in part, because Vanessa is just as crazy and just as quick as Wade is. She has no problem matching miseries with him in the middle of a seedy bar. She also makes it clear from the get-go that she can handle herself. When another bar patron gets fresh with her and Wade tries to intervene, Vanessa steps in and handles the jerk herself, grabbing him in a very sensitive area and demanding an apology:
VANESSA: Say the magic words, Fat Gandalf.
BUCK: I'm sorry.
Vanessa brings that fighting spirit to Wade's cancer diagnosis, too. While Wade is cynical and accepting of his fate, Vanessa gathers brochures for far-off clinics trying experimental treatments. Things may get nasty, but she doesn't plan on going anywhere—and she doesn't plan on letting Wade disappear, either:
VANESSA: …You're not going anywhere. Drink.
Vanessa hands him a glass.
WADE: You're right. Cancer is only in my liver, lungs, prostate, and brain. All things I can live without.
He drinks. It tastes terrible.
VANESSA: You belong here at home, surrounded by your Voltron and your Bernadette and your me.
That doesn't stop Wade from leaving, of course, and Vanessa herself disappears from the narrative almost entirely at that point. When Wade first tries to reconnect with her in the film's final act, we learn that she's working as a waitress in a strip club, and Wade bails on talking to her. So much for not being a short-shorted, two-dimensional sex object.
The Princess is in Another Castle
The narrative doubles down on its diminishment of Vanessa when Ajax kidnaps her and holds her hostage at the shipyard. Ajax locks her into the torture tank, and we see her suspended there like a carrot for Deadpool, catapulting her straight into the Comic Book Ladies in Peril Club, right alongside Mary Jane Watson, Vicki Vale, and Lois Lane. Vanessa may be able to quote the Star Wars trilogy at will, but for all of her geeky dream girl street cred, she's ultimately a flat character that manages to mix two film tropes into one attractive package: She's both a hooker with a heart of gold and a damsel in distress.