Can a character with zero strength make a challenge and win a power token for unopposed if the opponent has no characters on the table.
I know with zero strength, the challenge can't be "won" but how about for unopposed cause in a sense, there are no opposing characters to defend.
No, you can't claim an unopposed challenge if your attacking strength is zero. You have to actually WIN the challenge to claim the power for an unopposed challenge, and you can't win the challenge with a strength of zero. You must have a total strength of at least 1 to win a challenge as either an attacker or defender.