Duelbits — 24% effective
Highest published like-for-like cash rakeback in the dataset, with a worked formula and official VIP transfer route. Published 25% combined house-edge rakeback (formula with worked example on official blog), cash with no wagering, accruing from the first bet. 31 levels plus a Bronze/Silver/Gold VIP Club overlay; unclaimed level bonuses roll forward with no expiry. Official ceiling claim is 47.5% with milestones.
Watch out: Third-party 'up to 50%' is affiliate inflation — official copy tops out at 47.5% and is internally inconsistent. Per-level thresholds and VIP Club entry criteria are unpublished. Welcome free-spin stages expire 24h after crediting. Heavy KYC reported after large wins (one disputed $253k case).