Here is the full list of all 30 Jet Set Radio achievements. It takes around 30-35 hours to unlock all of the achievements on Windows.
Use all graffiti in missions
Unlock Pots and use him as a player character
Unlock all characters
Unlock all songs in the bonus menu
Unlock Goji and use him as a player character
Complete every level with a Jet rating in all game modes
Complete all missions with any rating
Unlock Love Shockers and use her as a player character
Collect all Graffiti Souls
Unlock Poison Jam and use him as a player character
Unlock non-masked Poison Jam and use him as a player character
Unlock Noise Tank and use him as a player character
Destroy all helicopters in a level
Draw graffiti 5 times on Onishima's back
Unlock Garam and use him as a player character
Complete Chapter 3
Finish the game without anyone latching onto you
Perform a 100+ trick combo
Complete Chapter 2
Complete Chapter 1
Tag at least one rival gang member within 30 seconds
Shove the two civilians in No. 540 level before the choppers show up
Complete a level without collecting a Recovery Spray Can
Make 100 civilians jump out of your way
Create your own graffiti in all sizes
Fall more than 20 meters off a building
Unlock Gum and Tab
Start the game for the first time
Complete the tuorial
Perform a Turn Trick in game