Super-Kings or Super King Chess or King of the Hill: which is the hardest variant?

The Super-Kings chess variant is where the King has all the powers of a queen and knight, and can move and capture exactly like a queen and knight. Outside of that, the same rules of chess still apply. Jose Raul Capablanca was a genius at these types of variants.  This fun variant has been played in different forms for quite some time now! It is being played a lot in chess clubs today!

Super King chess or Monster chess is a chess variant in which the White side has only a king and four pawns to fight against all the pieces of the Black side. All the rules of chess apply, except that White makes two successive moves per turn. The white king can move into check on the first move of the turn and move out of check during the second move. The goal for both sides is to checkmate the opponent's king.

A King of the Hill variant is a chess game where players win by either checkmating the opponent or by moving their king to one of the four central squares of the board. This variant keeps the standard rules of chess but adds this new victory condition, which emphasizes the importance of controlling the center of the board. 

Which variant is the most difficult to play? All these variants are so fun to play!