When I give myself an Iron Sword with +1024 Attack Speed, it makes me recover faster but it takes 20 hits to kill a skeleton wich means it deals half a heart of damage each hit, which isn't normal.

The command that I used:
give @p iron_sword 1 0 {display:

{Name:"Sword L-1",Lore:["The sword of the Hero!"]}

,CanDestroy:["minecraft:leaves2","minecraft:tallgrass"],Unbreakable:1,AttributeModifiers:[

{AttributeName:"generic.attackSpeed",Name:"generic.attackSpeed",Amount:1024,Operation:0,UUIDLeast:1,UUIDMost:1}

]}