Rebirth: My Dear Little Wife Is So Scheming - Chapter 20 - Myocardial Infarction

Some say reincarnation is a blessing, but for me, it's a dreadful curse. Cursed with endless reincarnation, I've been reborn as a villain 137 times. And all 137 times, I've been toyed with and killed by heroes who are far more cruel than the said villains... If I can't win no matter what I do, then I'll crush those so-called heroes at their very roots. - Quality Fan Translations, Made by Fans for the Fans - Villain Takes Over The Academy

After 2000 years has passed, the ruthless demon lord has just been reincarnated! But his aptitude at an academy for nurturing candidates for demon lords is, “Inept”!?

[WARNING R18+]In his previous life, the loser Li Long thanked God for giving him another chance to be reborn with his memories. And in an accident Li Long got a legacy left by a dual cultivator. So Li Long decided that from this life on, he would be good to himself and others, and vowed not to suppress the dark personality of his previous life. No matter if he was spit on by thousands of people or was not tolerated by the world, he would live only for himself in the future...

After Reincarnating into Naruto World at the Warring State Era as an Uzumaki, Masahiko thought that he got a useless System. He lived for 48 years as a normal, below average Uzumaki Shinobi.

That changed when he finally knew how the system works the day of his 49th Birthday!

- Description from Novelupdates