Attack.
Hero Response (attack): After you defend against an enemy attack and take no damage, deal damage to that enemy equal to your DEF for that attack.
One of my favorite new cards to try and make work, with the right hand and tucked cards, Silk can get this to 10+ damage and it's one of those plays where when you pull it off, you feel like a master card game player.
Goes well with 'never back down' which allows you to get +2 DEF and then if you take no damage -> stun the enemy + damage him for your DEF+2 value. Works great with the stun-lock deck of captain America
Just managed an 18 damage play with this card and Gambit in Protection...Had Natural Agility, 2 x Expert Defense cards, a double resource and "Stop Hitting Yourself" in my hand.
Gambit had 8 charge counters after playing Natural Agility...and with Expert Defenses and an Armor Vest...he was defending for 18!!
Actually ended up with those five cards in my hand the previous turn (after some card draws)....decided to just keep them at the end of the player phase...it felt GLORIOUS!