2x Damage Card
The 2x Damage Card doubles a players damage for 20 minutes. This is accomplished by multiplying what you would hit by 2, rather than merely increasing your max hit by 2 times.
The card is obtainable from the following boxes and Chests;
Black Diamond Box
2K21 Box for Sponsor, Executive and Platinum Players receive 2.5x Damage Card and 10% Drop Rate Card respectively.
Yu-Gi-Oh Box
Event GoodieBox
Vending Machine
Slayer Chest
The card is obtainable from the following bosses;
The Nightmare, Vote boss, Sponsor Dragon, Miss Fortune, Bomberman, Crimson Chin, and Lachrym The Undying
The card is obtainable from the following shops;
Executive Shop, Platinum Shop, Slayer Shop, Item Grinder Rewards Shop and also through the Redemption Web Store.
The 2.5x Damage Card is a card, useable for 20 minutes, which gives an even more insane boost to your damage! Instead of your "regular hits", everything is done x2.5!
Which is a reason why the card is commonly used for Raids / Team Bosses / Arcade / ...
The card is obtainable by upgrading the 2x Damage Card or you can possibly get it from the 2K21 Box.