how much damage does a 2/2 doublestrike do

[Batassassin]

how much damage does a 2/2 double strike do

[Arix]

It would do 2 damage twice, usually for a total of 4.

Note that this can be different if it's blocking or blocked by a creature with 2 or less toughness, in which case it will deal 2 to that creature, killing it, then it won't deal any more.

[Batassassin]

why not

[Arix]

Because there's nothing for it to deal damage to.

[Batassassin]

ok then I'll deal the damage i'm owed to the player?

[Arix]

No you won't. Once the creature has become blocked, it's blocked. It won't deal any damage to the defending player unless it has trample or an ability such as Thorn Elemental's.