If I kill Scuttle Crab with Nidalee, do I draw first or do I show my hand first?

According to the RiftJudge FAQ #10347, Scuttle Crab's Deathknell ability resolves completely before Nidalee, Cat Form's draw ability triggers.

You do not draw first; the opponent will be forced to reveal their hand for the Deathknell before the game acknowledges that Nidalee has won the combat and triggers her draw ability.

The Sequence of Events (Rule 461.1, 461.2):

1. Combat Cleanup: Scuttle Crab takes lethal damage. Its Deathknell triggers as a "Pending Item."
2. First FEPR Window: Scuttle Crab's Deathknell is placed on the chain and resolves. Your opponent reveals their hand at this moment.
3. Determine Combat Result: The game determines the winner of the combat. Since Scuttle Crab was defeated and Nidalee remained, Nidalee is declared the winner. This triggers her "When I win a combat, draw 1" ability as a new "Pending Item."
4. Second FEPR Window: Nidalee’s draw ability is placed on the chain and resolves, and you draw your card.

Because these abilities are processed in separate FEPR (Finalize, Execute, Pass, Resolve) windows, the reveal happens entirely before Nidalee's draw effect even begins to trigger.