Existence

Briefly about Existence manga:

One day, it was a herd of ants, on another, it was a large dinosaur. This was the last reincarnation of a being that had experienced tens of thousands of lives.
Now, he was born as a human with the power of every single lifeform he had ever been.

Existence manga.

Why did he have such an ability? Lee Jain finally came to an answer.
“I exist to eradicate mankind.”