Start with the Mangekyo Sharingan: Follow Lord Madara out of Konoha - Chapter 221 - 114: Space-Time Barrier

Transported to the chaotic era of warlord conflicts, Xu Guang is displaced and ends up begging.By chance, he lands a job in a rich family, responsible for taming the mammoth.[Name: Xu Guang][Current Job: 1. Beggar Lv5 (50/600). 2. Elephant Envoy Lv0 (50/100)][Professional Talent (Elephant Envoy): Enchantment (When you form a bond with your closest Giant Elephant partner, you will receive the elephant's favor and your strength will be amplified by the Giant Elephant)]

Gripes have their origins and debts have their creditors. We haven’t crossed each other in days past or present, nor formed any grudges. I am but duty-bound to carry this out, so apologies in advance!

In his past life, Yang Chen was a gentle person who was oppressed for his whole life.

Now that he’s reborn, he chose to become an executioner and severs ties and grudges with his executioner’s blade, killing all that climb onto the Immortal Executioner’s Platform!

Heads will roll! Humans’ in the human realm, demons’ in the demon realm, devils’ in the devil realm and immortals’ in the immortal realm!

- Description from novelupdates

“Who are you lady?”

“How rude I am the goddess of reincarnation!”

A normal young man found himself surrounded by thousands of gods who were observing him silently.

“Shit... did I die?”

“yes... I know it must be hard-”

“LET'S GO GIVE ME MY HAREM AND OP ABILITIES LET ME EXPERIENCE COCKY EGOTISTICAL PEOPLE WHO WILL CALL ME TRASH NO MATTER HOW MUCH I PROVE I'M OVERPOWERED!!!”

Dead silence... Thousands of gods were left speechless.

“ok give me my system or infinite magic or unique bloodline or whatever”

Hearing what the young man said thousands of gods burst into laughter.

“I the God of strength will give you my system”

“I the God of life will give you my system”

“I the God of archery will give you my system”

Every single god gave the young man their system/power causing a unique system to be made just for him.

[Supreme System]

Traversing into another world, Zhang Xuan finds himself becoming an honorable teacher.

Along with his transcension, a mysterious library appears in his mind.

As long as it is something he has seen, regardless of whether it is a human or an object, a book on its weaknesses will be automatically compiled in the library.

Thus, he becomes formidable.

“Emperor Zhuoyang, why do you detest wearing your underwear so much? As an emperor, can’t you pay a little more attention to your image?”

“Fairy Linglong, you can always look for me if you find yourself unable to sleep at night. I am skilled in lullabies!”

“And you, Demon Lord Qiankun! Can you cut down on the garlic? Are you trying to kill me with that stench?”

This is an incredible story about teachers and students, grooming and guiding the greatest experts in the world!

- Description from Novelupdates