I would say it is very premature to speak in terms of all-time greatness with Vasyl Lomachenko. Longevity is certainly a factor in determining who receives this type of label. He is an elite boxer of the current day who has great potential and could certainly achieve monumental things if he stays on the current course but based on all the criteria we use to determining all-time greatness, he is a good ways away from receiving that type of acclaim just yet.
But there still begs the question, how do you beat him? Outside of landing one single knockout blow, defeating Loma is going to be a monumental task for any fighter today. It would seem to me that it takes one of two kinds of fighters to beat him.