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 https://mangabtt.com 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.” Released