Is the 33x33 the hardest Rubik's cube

[povlhp]

Bandaged cubes are harder. Mastermorphix is difficult to wrap you head around.
Now we just need a 4-5 layer Sq-1 to make the game even more fun. New algorithms would have to be invented.

 

[Cubing Forever]

Now we just need a 4-5 layer Sq-1 to make the game even more fun. New algorithms would have to be invented.

idk if this is available anymore

 

[Deleted member 36445]

So there's this guy on quora that gave some examples...

Maltese Gears Cube

"Mixing a Geared Mixup and Void Cube this is a real challenge. I would also keep an eye on the prodigious output of Oskar van Deventer who tries to create a new puzzle every day!"

Latch Cube

"One of the trickiest of the constrained cubes. A 3x3 with faces that will only turn in the direction of any arrows on them. Have arrows facing in more than one direction on a side? Congratulations. That side is now locked!"

Eitan’s Star (Couldn't find a working link for this one...)

"An Icosahedron shaped puzzle. Takes a long time to solve."

Clover Octahedron Fragmentation

"An Octahedron shaped puzzle. The hardest of the Clover cubes."

 

[Cubing Forever]

there's also this:
Geranium, puzzle (verypuzzle.com)

 

[StrategySam]

A really hard cube is the apple cube. The difficult part is that the center change if you do any move.