'Spottedleaf, if you could kill any leader that is NOT in the Dark Forest, who would it be?'

From Glaceon-lucario

Well, I came up with a lot of leaders until you said- 'that is NOT in the Dark Forest'

Does Scourge count? He was basically the leader of BloodClan.

If that doesn't count, then Blackstar. He was persuaded by a loner to forget about his ancestors! Like, seriously?!