Ultimate King of the G.F.B.s

''Against all odds, you are invincible. You have beaten the game and unlocked access to the Infinite Wave. People shall remember you for centuries to come. Difficulty: Impossible.''

This achievement is gained when you get to F.A.I.L. and S.A.F.E. without having lost a single life. F.A.I.L. and S.A.F.E. say that you have passed the test of awesomeness, and they just move on by without you having to fight them. You get to round 751, which lasts for an infinite duration. You can skip to round 751 at any time. You get 1 million Monkey Money and unlock everything, including premium stuff.