Here is the full list of all 14 Round 99 achievements.
Get over 100 kills!
Get over 1000 kills!
Get over 9000 kills!
Gain 1000 points in Endless Mode!
Gain 10000 points in Endless Mode!
Gain 100000 points in Endless Mode!
Complete a level!
Have all 12 levels unlocked!
Complete every level in the game!
Purchase all weapons!
Purchase every upgrade for every weapon!
Purchase all health and armor upgrades!
Play a multiplayer match!
Beat Arcade Mode!