The Hell Stab is the strongest technique of the Third Raikage, whereby he concentrates a considerable amount of lightning chakra into just the finger-tips of a single hand and then performs a thrusting motion, which together allows him to pierce a target in a manner somewhat similar to either the Chidori or Lightning Cutter.
The intensity, size and strength of the technique can be proportionally increased by reducing the number of fingers involved:
Four-Finger Nukite (四本貫手, Yonhon Nukite): Strong enough to break through robust defences with relative ease.
Three-Finger Nukite (三本貫手, Sanbon Nukite): Effective against even malleablematerials that can usually handle a blow by dissipating its force.
One-Finger Nukite (一本貫手, Ippon Nukite): Known as the "strongest spear" (最強の矛, saikyō no hoko), where the concentration of chakra is so great that it extends well beyond the finger in a lone point. It was capable of cutting off all of Gyūki's tails during an encounter, and was capable of piercing even the Third's Lightning Release Armour, and left a scar on his body, which due to its ability to his immense durability was regarded as the "strongest shield" (最強の盾, saikyō no tate).
A nukite (貫手, Literally meaning: crossbeam hand) is a move used in martial arts like karate, where you strike the opponent with your finger stretched out. A four-finger nukite (四本貫手, yonhon nukite) uses the four fingers and, when aimed at the throat, is called a hell stab (地獄突き, jigokuzuki). The two-finger nukite (二本貫手, nihon nukite) and one-finger nukite (一本貫手, ippon nukite) are also used. A three-finger nukite (三本貫手, sanbon nukite) seems to be somewhat rare.