who is the most jain person ever

In Jain understanding, the highest and most complete embodiment of Jain ideals is a Tirthankar, and among them Lord Mahavir Swami is the most well-known and revered for fully practicing and teaching the path of Ahimsa, Satya, Aparigraha, Brahmacharya, and non-attachment.

So, if you mean “who best represents Jain Dharma?”, the answer is:

Lord Mahavir Swami.

In the deepest sense, though, Jainism teaches that the goal is not to rank people, but to follow the path toward purification of the soul.