Jigoku「地獄」 is a special case of tanki wait where two of the winning tiles are already visible to all the players.
Wait strength
Aside from karaten, this is the weakest choice for a wait, because of the number of available tiles to win: one. However, the solitary tile may actually be strong, as players may view it as a safe tile; and therefore, one player may discard it. The wait would be better still with the addition of suji and/or kabe, or even with an honor tile with two already discarded. In essence, choosing this wait may come in the form of a trap, luring unsuspecting players. This wait is best used for emergency situations, such as being in last place at oorasu and other dire circumstances.