Gonna leave this here, maybe some are interested. :D

What we need:
Money to buy the game you want
G2A Account
2 Steam / Origin Accounts

Method:
Buy the game you like with G2A Shield.
Redeem the key on the first account.
Go back to G2A and look for your order number for the key and get in a live chat.
Tell them that your key was already activated.
They will ask for proof that it's invalid. Now you need your second account. So go ahead and try to redeem the same key in steam or origin and make a screenshot.
Now they will offer you a refund. You will ask for a refund and the money will be on your G2A account instantly but locked for 14 days.

You can repeat this with different accounts as they will surely blacklist your account after too many refunds. :p