Here is the full list of all 20 No More Heroes achievements.
You have defeated "Henry"
You have defeated "Jeane"
Earned 9 Gold Medals on part-time jobs
You have defeated the Rank 2 Assassin "Bad Girl"
You have defeated the Rank 3 Assassin "Speed Buster".
You have defeated the Rank 4 Assassin "Harvey Moiseiwitsch Volodarskii".
You have defeated the Rank 5 Assassin "Letz Shake".
You have defeated the Rank 6 Assassin "Holly Summers".
You have defeated the Rank 7 Assassin "Destroyman".
You have defeated the Rank 8 Assassin "Shinobu".
You have defeated the Rank 9 Assassin "Dr. Peace".
You have defeated the Rank 10 Assassin "Death Metal".
Earned 20 Gold Medals on Assassination Missions
Earned 10 Gold Medals on Free Fight Missions
Used whatever means available to beat 510 regular enemies
Sweeter than you thought? Just like Sylvia!
Finished all of Ryu's instructions! You wanted THAT!
You somehow managed to visit every bathroom in Santa Destroy. Why don't you start living in one?
Collected 51 trading cards!
You have accomplished everything!