KC Free SR Card

What is the most worthy free SR card that you can claim after hitting Plat in the KC Tour?

Cards from Boosters are not allowed. You can take any SR card from Level-Up Reward, Trader, or LD Drops (including event LD).

LD Drops: Most useful, but can be easily obtained through other methods. (Would only consider Champion's Vigilance.)

Event LD Drops: Limited edition, but will likely be obtainable in the future and I have at least one copy of each. Do I really want a second Union Attack when one does the job?

Trader Cards: Not limited edition, if you really put in the grind work. Cerberus or Gravekeeper's Oracle would be the choice.

Expired Trader Cards: Includes Obnoxious Celtic Guard, Bad Reaction to Simochi, Catapult Turtle. Cannot be obtained any other way (as of right now). Not very useful, however.

Level Rewards: The only card here is Temple of the Kings. Is it worth getting a second copy? It's not that useful, but this is the only way.