FAQ
Can I use another card's "negate the effect of..." effect to negate the [Blocker] gained from this [Activate: Main] effect?
No, you cannot.
One Piece TCG [OP09]

Card Description
Activate: Main Once Per Turn If your Leader has the {Blackbeard Pirates} type, this Character gains Double Attack, Banish or Blocker until the end of your opponent's next turn.
Card Details
Rarity
UC
Color
Black
Number
OP09-084
Card Type
CHARACTER
Play Cost
5
Power
6000
Subtype(s)
Blackbeard Pirates
Attribute
Special
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Price History (USD)
Price Info
Market Price
$0.11
All time High (last 6 months)
$0.15
All time Low (last 6 months)
$0.07
No, you cannot.