Command Block Trouble

Lets simplify your command by removing all lot of data.

/give @p diamond_sword 1 0 {display:{...},AttributeModifiers:[{...},{ench:[{...}]}}

AttributeModifiers has no ] before the enchantment section. The enchantment section is contained in curly brackets and should not be. This would give us:

/give @p diamond_sword 1 0 {display:{...},AttributeModifiers:[{...}],ench:[{...}]}

The last thing, Slot:0b does not work with attribute modifiers to my knowledge. If you are wanting it to be in the main hand, the proper slot name is "mainhand"

Which would give us a final command of:

/give @p diamond_sword 1 0 {display:{Name:"Sword",Lore:["Smexy"]},AttributeModifiers:[{AttributeName:"generic.attackSpeed",Name:"generic.attackSpeed",Amount:100,Operation:1,UUIDMost:307,UUIDLeast:307,Slot:"mainhand"}],ench:[{id:16,lvl:10}]}

Which gives us this guy:

Minecraft commands expect every certain symbols to be paired with each other. In particular, every [ or { should be matched with a ] or }, respectively. These symbols work similarly to parenthesis in Mathematics, they indicate that their contents should be considered as a single item. So the error message Expected ']' but got '<EOF>' means that your command had a [ symbol, but Minecraft couldn't find a ] to go with it.

In your particular case, Minecraft couldn't find a ] to go with the [ found right after AttributeModifiers:. So you should add a ] after all the attributes; specifically, between the last two } characters. This results in the following command, which executes successfully:

/give @p diamond_sword 1 0 {display:{Name:"Sword",Lore:["Smexy"]},AttributeModifiers:[{AttributeName:"generic.attackSpeed",Name:"generic.attackSpeed",Amount:100,Operation:1,UUIDMost:307,UUIDLeast:307,Slot:0b},{ench:[{id:16,lvl:10}]}]}