Help, I can’t think of this word!!

[Chumssss]

Okay, not an Aibu really, but I am
desperately trying to think of a word. It describes someone who is an underdog, not expected to win, but inserted anyway and they run away with it etc. I feel it has a Q or a Z in it somewhere. I’ve tried lots of Google searches, but can’t get the right one to get the word. Can anyone help??

Hundred-to-one shot?

I can only think of Giant Killer.

Ooh another one - Rank Outsider?

Dark horse?

Dark horse

Everyman?

Ringer?

Wildcard?

Under dog?

Wild card?

Ringer

Sleeper?

Fluke? Stooge? Unknown Quantity?

Rank outsider

Antagonist or adversary?

Zero to hero 🤭

Boil over? (I think that's horses only)

moonshot?

Dark horse

Vanquish?

Bandit? Hustler? Chancer?

Qualifier
Incubent
Hazard

Outlier?

David (as in, vs. Goliath).

Could it be quisling, although that's more of a decoy?