One, three generations of Hokage
Although the three generations of Hokage had a soft heart and let him go once when the matter of Orochimaru's human experiments was revealed, when Orochimaru took advantage of the middle ninja exam to attack Konoha again, the three generations of Hokage made up his mind to get rid of this once most beloved disciple with his own hands. But it's a pity that due to the advanced age of the three generations of Hokage, there is not much chakra left, so he has always been at a disadvantage in the battle with Orochimaru, and in the end, even if the three generations fought for their own lives, they only died of exhaustion after sealing one of Orochimaru's hands.
Second, the fourth generation Hokage
As a result of witnessing Rin's death, Uchiha Obito gradually turned black and became very hateful to the world. And in order to create a world with only Rin, Obito actually ignored the life and death of his master Jiu Xinnai, and released the Nine-Tails when he gave birth. Although the four Hokages later appeared in time, defeated Obito and sealed the Nine-Tails in Naruto's body, after this incident, the four Hokage and his wife also died.
Three, self-come
Although Jirai also had high hopes for Nagato, who had the eye of reincarnation, but after Yahiko's death, Nagato gradually blackened, so when Jiraiya went to Rain Ninja Village to collect information many years later, Nagato didn't care about the former master and apprentice at all, and directly used his six doppelgangers to brutally kill Jiraiya.
Fourth, the Great Snake Pill
In order to get Sasuke's body, Orochimaru not only induced Sasuke to leave Konoha and join his own disciples, but also gave him careful teaching during the period when Sasuke defected to him, so that his strength improved by leaps and bounds. However, what Orochimaru never expected was that although he had cultivated Sasuke well, before he could take it, Sasuke took the lead and killed him when he was at his weakest. Although, with enough back-hands, Orochimaru was eventually resurrected again, it can be seen from the above events that Konoha's tradition of killing teachers is in the same line.