The Naruto Ninjutsu That's A Blessing And A Curse To Its Target
Among the scores of shonen anime out there, few have battle systems quite as varied as the jutsus of "Naruto." Performed through the use of a spiritual energy known as chakra (often in combination with specialized hand positions), these quasi-magical spells can perform a wide variety of different tasks. A well trained ninja in the "Naruto" universe can do anything from casting illusions, to summoning animals, to creating clones of themselves from pure shadow. However, the act of casting fancy ninja magic isn't always as fun as it sounds on paper. Just like any other tool for combat, jutsus can be quite dangerous.
Many of these are, of course, forbidden jutsu, which are generally considered harmful enough to be banned in shinobi societies. However, even some of the socially acceptable jutsu out there can bring serious harm to the user or others. One ninjutsu in particular is both a blessing and a curse to its target.
Tsunade's Creation Rebirth trades time for health
While it is far from the only jutsu that is a double edged sword, Lady Tsunade's Creation Rebirth Jutsu might just take the cake in terms of benefits compared to the drawbacks. Unlike other self-damaging jutsu, Creation Rebirth actually heals its target by accelerating cell division. This is so efficient at healing people that it is often called "the pinnacle of medical ninjutsu." The tradeoff, however, is quite steep.
As your high school biology textbook can tell you, a cell can only divide a certain number of times before it can no longer reproduce (via ScienceDirect). This is known as the Hayflick Limit, which correlates heavily with aging and is just one of the reasons that everything inevitably dies. Disregarding the existential horrors of mortality, however, the same basic concept applies in "Naruto." Since Creation Rebirth only heals by accelerating the rate at which cells divide, it effectively shortens the lifespan of the target. The more severe the injury, the more cells have to divide and the less time the target has left to live.
That said, there are many other jutsus out there with drawbacks that make Creation Rebirth seem optimistic in comparison. If heroically shuffling your way off this mortal coil as fast as possible is your goal, then there are a few jutsus that can definitely help with that.
There are so many jutsu that just straight up kill you
Let's not beat around the bush any longer. Justus that hurt the user, such as Creation Rebirth or Mangekyo Sharingan, are nothing compared to the ones that straight-up kill whoever uses them. The most famous of these is the Dead Demon Consuming Seal, which the Fourth Hokage used to seal the Nine-Tailed Fox inside of Naruto. When the Third Hokage used it against Orochimaru in "Naruto" Episode 72, it is revealed that the jutsu actually summons a death god to seal away the user's target in exchange for their life.
Conversely, the justus One's Own Life Reincarnation and Outer Path — Samsara of Heavenly Life Technique both allow the user to bring someone back from the dead at the cost of their own life. These jutsu thus far are rarely ever used — but there is one self-destructive taijutsu technique that is used quite often.
The Eight Gates are eight key points within every person's chakra network. Through training and determination, a skilled taijutsu user can "open" these gates to greatly increase their speed and power. When faced with tough enemies, taijutsu specialists like Rock Lee and Might Guy use this quite often. If they choose to open all eight gates, however, the stress on their body will become too much and they will eventually die without help from a very specific jutsu called the Yin-Yang Release. Luckily, that's one jutsu that causes no deaths whatsoever.