DEAD OR ALIVE 4

beat a player who is in the middle of a 20 or more win streak.

any easy way to do this is to set up a vs match (offline) with one round win. sign in a second player and kill the profile you want the achievements on 20 times. after this, go to your main profile and kill the second player.

If you have done the right you will get a message saying you have got a gold star.

after that go online and play a match to get the gold star

Very easy to do. You will need 2 controllers for this.

Go into settings and set health for versus at lowest and 1 round. This will speed things up!

Set up a versus mode, your account as player one and don't sign in as player 2. Take the player 2 controller and win 20 times in a row.

On the 21st round, take control of the player 1 controller (with your account) and win once. A pop up will occur saying "You have won a gold star". No achievement will unlock though.

Head to the DOA Online section and go quick match. You should be able to join a match. Do so, hopefully you won't have to play because there is one in play. Watch the match and when it ends your achievement will pop up. Now quit the match.

Hope this helped.

I want to add something to atheistium's and Button Masher's solutions. The GOLD, SILVER and BRONZE stars are stackable!
I made BRONZE star using above method, then I quit the VS Match (don't go into Xbox Live yet!).
Then I made SILVER star (using the same method) and quit.
Then I made GOLD (if those were not stackable, I could get the biggest one, you know)... and quit.
Log into DOA Online, find a match and watch it (or fight it). In the end of one only match you can get all 3 stars for the price of ONE Xbox Live match!