Superflip pattern: moves for a 3x3 cube
Every corner is solved and every edge is in its place but flipped. It is the best known hard position: it needs at least 20 moves to undo.
Moves
U R2 F B R B2 R U2 L B2 R U' D' R2 F R' L B2 U2 F2
20 moves, starting from a solved 3x3 cube.
Source: www.cubelelo.com