Here is the full list of all 100 Master Arena achievements.
Do 100 frags.
Do 75 frags.
Do 50 frags.
Do 2 double kill.
Do a headshot.
Do 10 kills without dying !
Do 20 kills without dying !
Good job!
Do your first Double kill!
Do your first Triple kill!
Do 5 kills without dying !
Do 10 frags.
Do your first Air-Rocket.
Do your first combo.
Do the first frag !
Welcome to Master Arena!
Do 100 headshots !
Do 100 "Double Kill" !
Do 75 "Triple Kill" !
Do 50 "Killing Spree" !
Do 25 "Insane" !
Do 20 "Infernal" !
Do 10 "Frantic" !
Do 5 "BOSSLIKE" !
Do 150 Frags.
Do 200 Frags
Do 250 frags.
Do 500 frags.
Do 750 frags.
Do 1000 frags.
Do 2500 frags.
Do 5000 frags.
Do 7500 frags.
Unbelievable!
Do 10 headshots.
Do 25 headshots!
Do 50 headshots!
Do 250 headshots.
Do 500 headshots.
Do 750 headshots.
A beautiful collection!
Do 5 Air-Rockets!
Do 10 Air-Rockets!
Do 20 Air-Rockets!
Do 30 Air-Rockets!
Do 40 Air-Rockets!
Do 50 Air-Rockets!
Do 60 Air-Rockets!
Do 70 Air-Rockets!
Do 80 Air-Rockets!
Do 90 Air-Rockets!
Do 100 Air-Rockets!
Do 5 combos.
Do 10 combos.
Do 20 combos.
Do 30 combos.
Do 40 combos.
Do 50 combos.
Do 60 combos.
Do 70 combos.
Do 80 combos.
Do 90 combos.
Do 100 combos.
Do 10 double kill.
Do 25 double kill.
Do 50 double kill.
Do 75 double kill.
Do 5 triple kill.
Do 10 triple kill.
Do 25 triple kill.
Do 50 triple kill.
Do your First Killing Spree!
Do 5 Killing Spree.
Do 10 Killing Spree.
Do 25 Killing Spree.
Do your first INSANE
INSANE x2
INSANE x3
INSANE x4
INSANE x5
INSANE x10
INSANE x15
INSANE x20
INFERNAL x1
INFERNAL x2
INFERNAL x3
INFERNAL x4
INFERNAL x5
INFERNAL x6
INFERNAL x7
INFERNAL x8
INFERNAL x9
INFERNAL x10
INFERNAL x15
FRANTIC x1
FRANTIC x2
FRANTIC x3
FRANTIC x4
FRANTIC x5
FRANTIC x6