Existence is a Manga/Manhwa/Manhua in (English/Raw) language, Action series, english chapters have been translated and you can read them here. You are reading chapters on www.mcreader.net fastest updating comic site. The Summary is
One day, it was a herd of ants, and another day, it was a large dinosaur.
This was the last reincarnation of a being that had experienced tens of thousands of reincarnations and lives.
He was born as a human with the power of every single lifeform he had ever been.
Why did he have such an ability?
Lee Jain finally came to understand.
“I exist to eradicate mankind.”