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 the tails of the Eight-Tails and piercing even the Third's Lightning Release Armour and own body, which due to its ability to withstand any technique 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.