Kaizo Mario (Asshole Mario as it's some times called) is arguly the most hardest Super Mario Hack ever.

Kaizo Mario World is a rom hack of Super Mario World which requires strategy, patience and concentration as it's know for Invisible blocks, almost impossible jumps, little time,Kaizo traps (in which you need to activate a blue P-switch to continue the level) and so much more.

Kaizo Traps are endings of the levels that kill you before you end the level and have a line of coins to show it's a trap.
The only way to stop a Kaizo Trap is a blue P-switch.

There are also Reverse Kaizo Traps in which there are a line of coins but in stead of falling or dieing there are platforms at the bottom most likely you will not see the platforms and if you use the P-switch you will go out of the range of the platform and die.

One of the most famous Let's Play User Proton Jon attempted Kaizo Mario World and During Special Stage 2 he spawned many memorable quotes as such

Proton Jon: Ok what do we got, I got 100 SECONDS!?!?
Jon: Fuck (savestate) fuck (savestate)fuck(savestate)fuck (savestate) fuck (savestate)fuck(savestate)fuck
(savestate)fuck(savestate)fuck(savestate)fuck(savestate)fuck(savestate)fuck(savestate)fuck(savestate)
fuck(savestate)fuck(savestate)fuck(savestate)fuck(savestate)fuck(savestate)fuck(savestate)fuck(savestate) FUCKING HELL
Jon: MOVE FASTER POKEY! FASTER! ……FASTER! FOR THE LOVE OF GOD FASTER!!!!
Jon: FOR THE LOVE OF BATMAN JUMP!!!!!… BILL COSBY IS ANGRY!!!! STIMPY!! I NEED SPACKLE!!!!
Jon: FUCK YOU SPECIAL STAGE FUCK YOU THERE I GOT FUCKING PISSED ARE YOU HAPPY?!?!
STATE SAVE STATE SAVE STATE SAVE!!!!!
Jon:WHO THE FUCK DESIGNED THIS GAME?!?
Jon:god damn JAPANESES WHAT IS WRONG WITH YOU?!? CAN'T YOU DESIGN A GOOD FUCKING GAME?!?!
Jon: 9,8,7,6,5,4 fuck you Yoshi (hits invisible coin block) AWWWWWWWWWWWWWWWWWW WAT?!!
Jon: (falls in the Kaizo Trap)Oh…what?! …WHAAAT?! WHAT?! …What the fuck? What the fuck? What…the…fuck? What the… (sobs)