Does Overzealous Fan make me pay Deflect when I kill it to move enemy unit to the base?

Yes, you must pay the Deflect cost if you choose to target an enemy unit that has the Deflect keyword with Overzealous Fan's ability.

According to RiftJudge FAQ #8505, the interaction works as follows:

1. Triggering: When Overzealous Fan gains the Defender designation, its ability triggers and is placed on the chain.
2. Targeting: You must choose the target (the attacking unit you intend to move) at the time you place the ability on the chain.
3. Deflect Cost: Because the ability chooses a unit, if that unit has Deflect, you are required to pay the Deflect cost at the time you place the ability on the chain.
4. Resolution: If you successfully pay the cost and place the ability on the chain, the ability resolves later. Only at the moment of resolution do you make the choice of whether to "kill" the Overzealous Fan to complete the effect.

Summary of Key Points:

• Targeting vs. Cost: The targeting (which requires paying Deflect) happens when the ability is placed on the chain. The "kill me" portion is a cost-within-instruction that is only paid upon resolution.
• Mandatory Cost: If you cannot pay the Deflect cost, you cannot legally choose that unit as a target for the ability.