Doflamingo for sure... He turned out to be just a low level scammer.
Oda will now have to think about what he should keep the secret which doflamingo knew. Because nothing seems that useful from story telling perspective at this point.
And the more important he tries to make the secret... It would lead to more plot holes for him.... I would say he better just hope to try to forget it like BM and Elbaf connection (including with fat loki proposing to Lola)