Here is the full list of all 20 Omega Blade achievements.
Welcome onboard. You completed succesfully the Arrival challenge.
You completed with victory the Big Weapon challenge.
You completed succesfully the Shinobi challenge.
You completed succesfully the Max Pain challenge.
You completed succesfully the Hurry Up challenge.
You completed succesfully the Sniper Wolf challenge.
You completed succesfully the Rainbow Guns challenge.
You completed succesfully the Shinobi Revenge challenge.
You completed succesfully the Sniper Master challenge.
You completed succesfully the The Ring challenge.
You completed succesfully the Into The Grid challenge.
You completed succesfully the Target Frenzy challenge.
You completed succesfully the Ring Return challenge.
You completed succesfully the Hyper Grid challenge.
You completed succesfully the Target Marathon challenge.
You completed succesfully the Strike Back challenge.
You completed succesfully the Walking Menace challenge.
You completed succesfully the Cqc Survivor challenge.
You completed succesfully the Safe Zone challenge.
You completed succesfully the Dual Blade challenge.