Shin-Zantetsuken

Shin-Zantetsuken, also known as Shin-Zantetsu and True Edge, is a recurring ability in the series. It is generally an upgrade to the signature attack Zantetsuken, and generally has a much higher chance to inflict Instant Death to all enemies than Zantetsuken. It has a success rate of 140 and stalls target's Final Attack one turn.

Final Fantasy VI
Shin-Zantetsuken, originally called True Edge, is the summon ability of Raiden. It has a higher success rate of inflicting Death to all enemies compare to Odin, and costs 80 MP to use.

Final Fantasy X-2
Shin-Zantetsu is an ability of the Samurai dressphere. It attempts to inflict Instant Death to all enemies instead of one enemy for the cost of 32 MP. This ability fails when an enemy is immune to the status ailment KO. It requires 100 AP to learn and requires Momentum to have been mastered. Learning the ability will unlock Zantetsu. It can also be used via Lady Luck's Attack Reels by rolling three Red 7s.

Final Fantasy XIV
Shin-Zantetsuken is Odin's final ability featured in the instanced encounter that debuted at FFFXIV FanFest 2014. Odin will begin to use Shin-Zantetsuken at around 20% HP, and the party must defeat him before the ability finishes casting, or else face certain death.

Final Fantasy Trading Card Game
The Raiden card references Shin-Zantetsuken by Breaking two Forwards when played, acting as an upgrade to the effects of Odin's cards, which Break one Forward.

Etymology
Shin-Zantetsuken involves a pun. 'Shin' could mean 'true' or 'new' meaning that an alternate name for Shin-Zantetsuken could read as "New Iron Cutting Sword" as an indicator of its upgraded form.