I had trouble on lv.986054. See, the huge robot building with 9999999999999999999999999 health was almost imposible to kill without the plasma rifle, chain gun, and 455653 rocket turrets. Oh, and to beat his second form in lv.12358798, you have to be lv.999 and have the heaven sword and the devels mace to kill him.
If you search: Whats the #1 cause of heart attacks, their will be a link that says: Play Tower of greed! One of the thousand free games on Kongregate.com!
 "Level Up!"){kind=icon}
 "Meat Boy (map pack)"){kind=icon}
 "The World's Hardest Game #2"){kind=icon}
 "You are a..."){kind=icon}
 "You Have To Burn The Rope"){kind=icon}
 "Meat Boy"){kind=icon}
 "Tower of Greed"){kind=icon}
 "Encompass"){kind=icon}
 "Leading Edge"){kind=icon}
 "Alpha Bounty"){kind=icon}
 "Medieval Rampage 2"){kind=icon}
 "Take Something Literally"){kind=icon}
 "Pillage the Village"){kind=icon}